diff --git a/.gitignore b/.gitignore
index 7b4c5d36cb4..bc324b5f826 100644
--- a/.gitignore
+++ b/.gitignore
@@ -109,13 +109,14 @@ Podfile.lock
 # IDE specific folder for JetBrains IDEs
 .idea/
 
-# Blaze files
+# Bazel files
 bazel-bin
 bazel-genfiles
 bazel-grpc
 bazel-out
 bazel-testlogs
 bazel_format_virtual_environment/
+tools/bazel-*
 
 # Debug output
 gdb.txt
diff --git a/BUILD b/BUILD
index 55c467edd53..0e2b9ee3a38 100644
--- a/BUILD
+++ b/BUILD
@@ -74,11 +74,11 @@ config_setting(
 )
 
 # This should be updated along with build.yaml
-g_stands_for = "gandalf"
+g_stands_for = "gale"
 
 core_version = "7.0.0"
 
-version = "1.21.0-dev"
+version = "1.22.0-dev"
 
 GPR_PUBLIC_HDRS = [
     "include/grpc/support/alloc.h",
@@ -997,6 +997,7 @@ grpc_cc_library(
         "src/core/lib/slice/slice_hash_table.h",
         "src/core/lib/slice/slice_internal.h",
         "src/core/lib/slice/slice_string_helpers.h",
+        "src/core/lib/slice/slice_utils.h",
         "src/core/lib/slice/slice_weak_hash_table.h",
         "src/core/lib/surface/api_trace.h",
         "src/core/lib/surface/call.h",
@@ -1561,20 +1562,6 @@ grpc_cc_library(
     ],
 )
 
-grpc_cc_library(
-    name = "grpc_resolver_dns_selection",
-    srcs = [
-        "src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.cc",
-    ],
-    hdrs = [
-        "src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.h",
-    ],
-    language = "c++",
-    deps = [
-        "grpc_base",
-    ],
-)
-
 grpc_cc_library(
     name = "grpc_resolver_dns_native",
     srcs = [
@@ -1584,7 +1571,6 @@ grpc_cc_library(
     deps = [
         "grpc_base",
         "grpc_client_channel",
-        "grpc_resolver_dns_selection",
     ],
 )
 
@@ -1614,7 +1600,6 @@ grpc_cc_library(
     deps = [
         "grpc_base",
         "grpc_client_channel",
-        "grpc_resolver_dns_selection",
     ],
 )
 
diff --git a/BUILD.gn b/BUILD.gn
index d3c1186f7a6..4454dc7220d 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -324,8 +324,6 @@ config("grpc_config") {
         "src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_libuv.cc",
         "src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_posix.cc",
         "src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_windows.cc",
-        "src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.cc",
-        "src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.h",
         "src/core/ext/filters/client_channel/resolver/dns/native/dns_resolver.cc",
         "src/core/ext/filters/client_channel/resolver/fake/fake_resolver.cc",
         "src/core/ext/filters/client_channel/resolver/fake/fake_resolver.h",
@@ -737,6 +735,7 @@ config("grpc_config") {
         "src/core/lib/slice/slice_internal.h",
         "src/core/lib/slice/slice_string_helpers.cc",
         "src/core/lib/slice/slice_string_helpers.h",
+        "src/core/lib/slice/slice_utils.h",
         "src/core/lib/slice/slice_weak_hash_table.h",
         "src/core/lib/surface/api_trace.cc",
         "src/core/lib/surface/api_trace.h",
@@ -1281,6 +1280,7 @@ config("grpc_config") {
         "src/core/lib/slice/slice_hash_table.h",
         "src/core/lib/slice/slice_internal.h",
         "src/core/lib/slice/slice_string_helpers.h",
+        "src/core/lib/slice/slice_utils.h",
         "src/core/lib/slice/slice_weak_hash_table.h",
         "src/core/lib/surface/api_trace.h",
         "src/core/lib/surface/call.h",
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 431afd40fce..8ba68c4a13b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -24,7 +24,7 @@
 cmake_minimum_required(VERSION 2.8)
 
 set(PACKAGE_NAME      "grpc")
-set(PACKAGE_VERSION   "1.21.0-dev")
+set(PACKAGE_VERSION   "1.22.0-dev")
 set(PACKAGE_STRING    "${PACKAGE_NAME} ${PACKAGE_VERSION}")
 set(PACKAGE_TARNAME   "${PACKAGE_NAME}-${PACKAGE_VERSION}")
 set(PACKAGE_BUGREPORT "https://github.com/grpc/grpc/issues/")
@@ -556,6 +556,12 @@ if(_gRPC_PLATFORM_LINUX OR _gRPC_PLATFORM_MAC OR _gRPC_PLATFORM_POSIX)
 add_dependencies(buildtests_cxx bm_call_create)
 endif()
 if(_gRPC_PLATFORM_LINUX OR _gRPC_PLATFORM_MAC OR _gRPC_PLATFORM_POSIX)
+add_dependencies(buildtests_cxx bm_callback_streaming_ping_pong)
+endif()
+if(_gRPC_PLATFORM_LINUX OR _gRPC_PLATFORM_MAC OR _gRPC_PLATFORM_POSIX)
+add_dependencies(buildtests_cxx bm_callback_unary_ping_pong)
+endif()
+if(_gRPC_PLATFORM_LINUX OR _gRPC_PLATFORM_MAC OR _gRPC_PLATFORM_POSIX)
 add_dependencies(buildtests_cxx bm_channel)
 endif()
 if(_gRPC_PLATFORM_LINUX OR _gRPC_PLATFORM_MAC OR _gRPC_PLATFORM_POSIX)
@@ -1301,7 +1307,6 @@ add_library(grpc
   src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_libuv.cc
   src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_posix.cc
   src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_windows.cc
-  src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.cc
   src/core/ext/filters/client_channel/resolver/dns/native/dns_resolver.cc
   src/core/ext/filters/client_channel/resolver/sockaddr/sockaddr_resolver.cc
   src/core/ext/filters/census/grpc_context.cc
@@ -2697,7 +2702,6 @@ add_library(grpc_unsecure
   src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_libuv.cc
   src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_posix.cc
   src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_windows.cc
-  src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.cc
   src/core/ext/filters/client_channel/resolver/dns/native/dns_resolver.cc
   src/core/ext/filters/client_channel/resolver/sockaddr/sockaddr_resolver.cc
   src/core/ext/filters/client_channel/resolver/fake/fake_resolver.cc
@@ -2906,6 +2910,67 @@ target_link_libraries(test_tcp_server
 )
 
 
+endif (gRPC_BUILD_TESTS)
+if (gRPC_BUILD_TESTS)
+
+if (gRPC_BUILD_CODEGEN)
+add_library(bm_callback_test_service_impl
+  ${_gRPC_PROTO_GENS_DIR}/src/proto/grpc/testing/echo.pb.cc
+  ${_gRPC_PROTO_GENS_DIR}/src/proto/grpc/testing/echo.grpc.pb.cc
+  ${_gRPC_PROTO_GENS_DIR}/src/proto/grpc/testing/echo.pb.h
+  ${_gRPC_PROTO_GENS_DIR}/src/proto/grpc/testing/echo.grpc.pb.h
+  ${_gRPC_PROTO_GENS_DIR}/src/proto/grpc/testing/echo_mock.grpc.pb.h
+  test/cpp/microbenchmarks/callback_test_service.cc
+)
+
+if(WIN32 AND MSVC)
+  set_target_properties(bm_callback_test_service_impl PROPERTIES COMPILE_PDB_NAME "bm_callback_test_service_impl"
+    COMPILE_PDB_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}"
+  )
+  if (gRPC_INSTALL)
+    install(FILES ${CMAKE_CURRENT_BINARY_DIR}/bm_callback_test_service_impl.pdb
+      DESTINATION ${gRPC_INSTALL_LIBDIR} OPTIONAL
+    )
+  endif()
+endif()
+
+protobuf_generate_grpc_cpp(
+  src/proto/grpc/testing/echo.proto
+)
+
+target_include_directories(bm_callback_test_service_impl
+  PUBLIC $<INSTALL_INTERFACE:${gRPC_INSTALL_INCLUDEDIR}> $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}
+  PRIVATE ${_gRPC_SSL_INCLUDE_DIR}
+  PRIVATE ${_gRPC_PROTOBUF_INCLUDE_DIR}
+  PRIVATE ${_gRPC_ZLIB_INCLUDE_DIR}
+  PRIVATE ${_gRPC_BENCHMARK_INCLUDE_DIR}
+  PRIVATE ${_gRPC_CARES_INCLUDE_DIR}
+  PRIVATE ${_gRPC_GFLAGS_INCLUDE_DIR}
+  PRIVATE ${_gRPC_ADDRESS_SORTING_INCLUDE_DIR}
+  PRIVATE ${_gRPC_NANOPB_INCLUDE_DIR}
+  PRIVATE third_party/googletest/googletest/include
+  PRIVATE third_party/googletest/googletest
+  PRIVATE third_party/googletest/googlemock/include
+  PRIVATE third_party/googletest/googlemock
+  PRIVATE ${_gRPC_PROTO_GENS_DIR}
+)
+target_link_libraries(bm_callback_test_service_impl
+  ${_gRPC_PROTOBUF_LIBRARIES}
+  ${_gRPC_ALLTARGETS_LIBRARIES}
+  grpc_benchmark
+  ${_gRPC_BENCHMARK_LIBRARIES}
+  grpc++_test_util_unsecure
+  grpc_test_util_unsecure
+  grpc++_unsecure
+  grpc_unsecure
+  gpr
+  grpc++_test_config
+  ${_gRPC_GFLAGS_LIBRARIES}
+)
+
+endif (gRPC_BUILD_CODEGEN)
+
 endif (gRPC_BUILD_TESTS)
 if (gRPC_BUILD_TESTS)
 
@@ -11549,6 +11614,98 @@ target_link_libraries(bm_call_create
 )
 
 
+endif()
+endif (gRPC_BUILD_TESTS)
+if (gRPC_BUILD_TESTS)
+if(_gRPC_PLATFORM_LINUX OR _gRPC_PLATFORM_MAC OR _gRPC_PLATFORM_POSIX)
+
+add_executable(bm_callback_streaming_ping_pong
+  test/cpp/microbenchmarks/bm_callback_streaming_ping_pong.cc
+  third_party/googletest/googletest/src/gtest-all.cc
+  third_party/googletest/googlemock/src/gmock-all.cc
+)
+
+
+target_include_directories(bm_callback_streaming_ping_pong
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include
+  PRIVATE ${_gRPC_SSL_INCLUDE_DIR}
+  PRIVATE ${_gRPC_PROTOBUF_INCLUDE_DIR}
+  PRIVATE ${_gRPC_ZLIB_INCLUDE_DIR}
+  PRIVATE ${_gRPC_BENCHMARK_INCLUDE_DIR}
+  PRIVATE ${_gRPC_CARES_INCLUDE_DIR}
+  PRIVATE ${_gRPC_GFLAGS_INCLUDE_DIR}
+  PRIVATE ${_gRPC_ADDRESS_SORTING_INCLUDE_DIR}
+  PRIVATE ${_gRPC_NANOPB_INCLUDE_DIR}
+  PRIVATE third_party/googletest/googletest/include
+  PRIVATE third_party/googletest/googletest
+  PRIVATE third_party/googletest/googlemock/include
+  PRIVATE third_party/googletest/googlemock
+  PRIVATE ${_gRPC_PROTO_GENS_DIR}
+)
+
+target_link_libraries(bm_callback_streaming_ping_pong
+  ${_gRPC_PROTOBUF_LIBRARIES}
+  ${_gRPC_ALLTARGETS_LIBRARIES}
+  grpc_benchmark
+  ${_gRPC_BENCHMARK_LIBRARIES}
+  grpc++_test_util_unsecure
+  grpc_test_util_unsecure
+  grpc++_unsecure
+  grpc_unsecure
+  gpr
+  grpc++_test_config
+  bm_callback_test_service_impl
+  ${_gRPC_GFLAGS_LIBRARIES}
+)
+
+
+endif()
+endif (gRPC_BUILD_TESTS)
+if (gRPC_BUILD_TESTS)
+if(_gRPC_PLATFORM_LINUX OR _gRPC_PLATFORM_MAC OR _gRPC_PLATFORM_POSIX)
+
+add_executable(bm_callback_unary_ping_pong
+  test/cpp/microbenchmarks/bm_callback_unary_ping_pong.cc
+  third_party/googletest/googletest/src/gtest-all.cc
+  third_party/googletest/googlemock/src/gmock-all.cc
+)
+
+
+target_include_directories(bm_callback_unary_ping_pong
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include
+  PRIVATE ${_gRPC_SSL_INCLUDE_DIR}
+  PRIVATE ${_gRPC_PROTOBUF_INCLUDE_DIR}
+  PRIVATE ${_gRPC_ZLIB_INCLUDE_DIR}
+  PRIVATE ${_gRPC_BENCHMARK_INCLUDE_DIR}
+  PRIVATE ${_gRPC_CARES_INCLUDE_DIR}
+  PRIVATE ${_gRPC_GFLAGS_INCLUDE_DIR}
+  PRIVATE ${_gRPC_ADDRESS_SORTING_INCLUDE_DIR}
+  PRIVATE ${_gRPC_NANOPB_INCLUDE_DIR}
+  PRIVATE third_party/googletest/googletest/include
+  PRIVATE third_party/googletest/googletest
+  PRIVATE third_party/googletest/googlemock/include
+  PRIVATE third_party/googletest/googlemock
+  PRIVATE ${_gRPC_PROTO_GENS_DIR}
+)
+
+target_link_libraries(bm_callback_unary_ping_pong
+  ${_gRPC_PROTOBUF_LIBRARIES}
+  ${_gRPC_ALLTARGETS_LIBRARIES}
+  grpc_benchmark
+  ${_gRPC_BENCHMARK_LIBRARIES}
+  grpc++_test_util_unsecure
+  grpc_test_util_unsecure
+  grpc++_unsecure
+  grpc_unsecure
+  gpr
+  grpc++_test_config
+  bm_callback_test_service_impl
+  ${_gRPC_GFLAGS_LIBRARIES}
+)
+
+
 endif()
 endif (gRPC_BUILD_TESTS)
 if (gRPC_BUILD_TESTS)
diff --git a/Makefile b/Makefile
index 847144bd874..ae125cb1aa5 100644
--- a/Makefile
+++ b/Makefile
@@ -460,8 +460,8 @@ Q = @
 endif
 
 CORE_VERSION = 7.0.0
-CPP_VERSION = 1.21.0-dev
-CSHARP_VERSION = 1.21.0-dev
+CPP_VERSION = 1.22.0-dev
+CSHARP_VERSION = 1.22.0-dev
 
 CPPFLAGS_NO_ARCH += $(addprefix -I, $(INCLUDES)) $(addprefix -D, $(DEFINES))
 CPPFLAGS += $(CPPFLAGS_NO_ARCH) $(ARCH_FLAGS)
@@ -1162,6 +1162,8 @@ bm_alarm: $(BINDIR)/$(CONFIG)/bm_alarm
 bm_arena: $(BINDIR)/$(CONFIG)/bm_arena
 bm_byte_buffer: $(BINDIR)/$(CONFIG)/bm_byte_buffer
 bm_call_create: $(BINDIR)/$(CONFIG)/bm_call_create
+bm_callback_streaming_ping_pong: $(BINDIR)/$(CONFIG)/bm_callback_streaming_ping_pong
+bm_callback_unary_ping_pong: $(BINDIR)/$(CONFIG)/bm_callback_unary_ping_pong
 bm_channel: $(BINDIR)/$(CONFIG)/bm_channel
 bm_chttp2_hpack: $(BINDIR)/$(CONFIG)/bm_chttp2_hpack
 bm_chttp2_transport: $(BINDIR)/$(CONFIG)/bm_chttp2_transport
@@ -1641,6 +1643,8 @@ buildtests_cxx: privatelibs_cxx \
   $(BINDIR)/$(CONFIG)/bm_arena \
   $(BINDIR)/$(CONFIG)/bm_byte_buffer \
   $(BINDIR)/$(CONFIG)/bm_call_create \
+  $(BINDIR)/$(CONFIG)/bm_callback_streaming_ping_pong \
+  $(BINDIR)/$(CONFIG)/bm_callback_unary_ping_pong \
   $(BINDIR)/$(CONFIG)/bm_channel \
   $(BINDIR)/$(CONFIG)/bm_chttp2_hpack \
   $(BINDIR)/$(CONFIG)/bm_chttp2_transport \
@@ -1788,6 +1792,8 @@ buildtests_cxx: privatelibs_cxx \
   $(BINDIR)/$(CONFIG)/bm_arena \
   $(BINDIR)/$(CONFIG)/bm_byte_buffer \
   $(BINDIR)/$(CONFIG)/bm_call_create \
+  $(BINDIR)/$(CONFIG)/bm_callback_streaming_ping_pong \
+  $(BINDIR)/$(CONFIG)/bm_callback_unary_ping_pong \
   $(BINDIR)/$(CONFIG)/bm_channel \
   $(BINDIR)/$(CONFIG)/bm_chttp2_hpack \
   $(BINDIR)/$(CONFIG)/bm_chttp2_transport \
@@ -2241,6 +2247,10 @@ test_cxx: buildtests_cxx
 	$(Q) $(BINDIR)/$(CONFIG)/bm_byte_buffer || ( echo test bm_byte_buffer failed ; exit 1 )
 	$(E) "[RUN]     Testing bm_call_create"
 	$(Q) $(BINDIR)/$(CONFIG)/bm_call_create || ( echo test bm_call_create failed ; exit 1 )
+	$(E) "[RUN]     Testing bm_callback_streaming_ping_pong"
+	$(Q) $(BINDIR)/$(CONFIG)/bm_callback_streaming_ping_pong || ( echo test bm_callback_streaming_ping_pong failed ; exit 1 )
+	$(E) "[RUN]     Testing bm_callback_unary_ping_pong"
+	$(Q) $(BINDIR)/$(CONFIG)/bm_callback_unary_ping_pong || ( echo test bm_callback_unary_ping_pong failed ; exit 1 )
 	$(E) "[RUN]     Testing bm_channel"
 	$(Q) $(BINDIR)/$(CONFIG)/bm_channel || ( echo test bm_channel failed ; exit 1 )
 	$(E) "[RUN]     Testing bm_chttp2_hpack"
@@ -3773,7 +3783,6 @@ LIBGRPC_SRC = \
     src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_libuv.cc \
     src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_posix.cc \
     src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_windows.cc \
-    src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.cc \
     src/core/ext/filters/client_channel/resolver/dns/native/dns_resolver.cc \
     src/core/ext/filters/client_channel/resolver/sockaddr/sockaddr_resolver.cc \
     src/core/ext/filters/census/grpc_context.cc \
@@ -5117,7 +5126,6 @@ LIBGRPC_UNSECURE_SRC = \
     src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_libuv.cc \
     src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_posix.cc \
     src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_windows.cc \
-    src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.cc \
     src/core/ext/filters/client_channel/resolver/dns/native/dns_resolver.cc \
     src/core/ext/filters/client_channel/resolver/sockaddr/sockaddr_resolver.cc \
     src/core/ext/filters/client_channel/resolver/fake/fake_resolver.cc \
@@ -5295,6 +5303,58 @@ endif
 endif
 
 
+LIBBM_CALLBACK_TEST_SERVICE_IMPL_SRC = \
+    $(GENDIR)/src/proto/grpc/testing/echo.pb.cc $(GENDIR)/src/proto/grpc/testing/echo.grpc.pb.cc \
+    test/cpp/microbenchmarks/callback_test_service.cc \
+
+PUBLIC_HEADERS_CXX += \
+
+LIBBM_CALLBACK_TEST_SERVICE_IMPL_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(LIBBM_CALLBACK_TEST_SERVICE_IMPL_SRC))))
+
+$(LIBBM_CALLBACK_TEST_SERVICE_IMPL_OBJS): CPPFLAGS += -Ithird_party/benchmark/include -DHAVE_POSIX_REGEX
+
+ifeq ($(NO_SECURE),true)
+
+# You can't build secure libraries if you don't have OpenSSL.
+
+$(LIBDIR)/$(CONFIG)/libbm_callback_test_service_impl.a: openssl_dep_error
+
+
+else
+
+ifeq ($(NO_PROTOBUF),true)
+
+# You can't build a C++ library if you don't have protobuf - a bit overreached, but still okay.
+
+$(LIBDIR)/$(CONFIG)/libbm_callback_test_service_impl.a: protobuf_dep_error
+
+
+else
+
+$(LIBDIR)/$(CONFIG)/libbm_callback_test_service_impl.a: $(ZLIB_DEP) $(OPENSSL_DEP) $(CARES_DEP) $(ADDRESS_SORTING_DEP) $(PROTOBUF_DEP) $(LIBBM_CALLBACK_TEST_SERVICE_IMPL_OBJS) 
+	$(E) "[AR]      Creating $@"
+	$(Q) mkdir -p `dirname $@`
+	$(Q) rm -f $(LIBDIR)/$(CONFIG)/libbm_callback_test_service_impl.a
+	$(Q) $(AR) $(AROPTS) $(LIBDIR)/$(CONFIG)/libbm_callback_test_service_impl.a $(LIBBM_CALLBACK_TEST_SERVICE_IMPL_OBJS) 
+ifeq ($(SYSTEM),Darwin)
+	$(Q) ranlib -no_warning_for_no_symbols $(LIBDIR)/$(CONFIG)/libbm_callback_test_service_impl.a
+endif
+
+
+
+
+endif
+
+endif
+
+ifneq ($(NO_SECURE),true)
+ifneq ($(NO_DEPS),true)
+-include $(LIBBM_CALLBACK_TEST_SERVICE_IMPL_OBJS:.o=.dep)
+endif
+endif
+$(OBJDIR)/$(CONFIG)/test/cpp/microbenchmarks/callback_test_service.o: $(GENDIR)/src/proto/grpc/testing/echo.pb.cc $(GENDIR)/src/proto/grpc/testing/echo.grpc.pb.cc
+
+
 LIBDNS_TEST_UTIL_SRC = \
     test/cpp/naming/dns_test_util.cc \
 
@@ -14495,6 +14555,94 @@ endif
 endif
 
 
+BM_CALLBACK_STREAMING_PING_PONG_SRC = \
+    test/cpp/microbenchmarks/bm_callback_streaming_ping_pong.cc \
+
+BM_CALLBACK_STREAMING_PING_PONG_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(BM_CALLBACK_STREAMING_PING_PONG_SRC))))
+ifeq ($(NO_SECURE),true)
+
+# You can't build secure targets if you don't have OpenSSL.
+
+$(BINDIR)/$(CONFIG)/bm_callback_streaming_ping_pong: openssl_dep_error
+
+else
+
+
+
+
+ifeq ($(NO_PROTOBUF),true)
+
+# You can't build the protoc plugins or protobuf-enabled targets if you don't have protobuf 3.5.0+.
+
+$(BINDIR)/$(CONFIG)/bm_callback_streaming_ping_pong: protobuf_dep_error
+
+else
+
+$(BINDIR)/$(CONFIG)/bm_callback_streaming_ping_pong: $(PROTOBUF_DEP) $(BM_CALLBACK_STREAMING_PING_PONG_OBJS) $(LIBDIR)/$(CONFIG)/libgrpc_benchmark.a $(LIBDIR)/$(CONFIG)/libbenchmark.a $(LIBDIR)/$(CONFIG)/libgrpc++_test_util_unsecure.a $(LIBDIR)/$(CONFIG)/libgrpc_test_util_unsecure.a $(LIBDIR)/$(CONFIG)/libgrpc++_unsecure.a $(LIBDIR)/$(CONFIG)/libgrpc_unsecure.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc++_test_config.a $(LIBDIR)/$(CONFIG)/libbm_callback_test_service_impl.a
+	$(E) "[LD]      Linking $@"
+	$(Q) mkdir -p `dirname $@`
+	$(Q) $(LDXX) $(LDFLAGS) $(BM_CALLBACK_STREAMING_PING_PONG_OBJS) $(LIBDIR)/$(CONFIG)/libgrpc_benchmark.a $(LIBDIR)/$(CONFIG)/libbenchmark.a $(LIBDIR)/$(CONFIG)/libgrpc++_test_util_unsecure.a $(LIBDIR)/$(CONFIG)/libgrpc_test_util_unsecure.a $(LIBDIR)/$(CONFIG)/libgrpc++_unsecure.a $(LIBDIR)/$(CONFIG)/libgrpc_unsecure.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc++_test_config.a $(LIBDIR)/$(CONFIG)/libbm_callback_test_service_impl.a $(LDLIBSXX) $(LDLIBS_PROTOBUF) $(LDLIBS) $(LDLIBS_SECURE) $(GTEST_LIB) -o $(BINDIR)/$(CONFIG)/bm_callback_streaming_ping_pong
+
+endif
+
+endif
+
+$(BM_CALLBACK_STREAMING_PING_PONG_OBJS): CPPFLAGS += -Ithird_party/benchmark/include -DHAVE_POSIX_REGEX
+$(OBJDIR)/$(CONFIG)/test/cpp/microbenchmarks/bm_callback_streaming_ping_pong.o:  $(LIBDIR)/$(CONFIG)/libgrpc_benchmark.a $(LIBDIR)/$(CONFIG)/libbenchmark.a $(LIBDIR)/$(CONFIG)/libgrpc++_test_util_unsecure.a $(LIBDIR)/$(CONFIG)/libgrpc_test_util_unsecure.a $(LIBDIR)/$(CONFIG)/libgrpc++_unsecure.a $(LIBDIR)/$(CONFIG)/libgrpc_unsecure.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc++_test_config.a $(LIBDIR)/$(CONFIG)/libbm_callback_test_service_impl.a
+
+deps_bm_callback_streaming_ping_pong: $(BM_CALLBACK_STREAMING_PING_PONG_OBJS:.o=.dep)
+
+ifneq ($(NO_SECURE),true)
+ifneq ($(NO_DEPS),true)
+-include $(BM_CALLBACK_STREAMING_PING_PONG_OBJS:.o=.dep)
+endif
+endif
+
+
+BM_CALLBACK_UNARY_PING_PONG_SRC = \
+    test/cpp/microbenchmarks/bm_callback_unary_ping_pong.cc \
+
+BM_CALLBACK_UNARY_PING_PONG_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(BM_CALLBACK_UNARY_PING_PONG_SRC))))
+ifeq ($(NO_SECURE),true)
+
+# You can't build secure targets if you don't have OpenSSL.
+
+$(BINDIR)/$(CONFIG)/bm_callback_unary_ping_pong: openssl_dep_error
+
+else
+
+
+
+
+ifeq ($(NO_PROTOBUF),true)
+
+# You can't build the protoc plugins or protobuf-enabled targets if you don't have protobuf 3.5.0+.
+
+$(BINDIR)/$(CONFIG)/bm_callback_unary_ping_pong: protobuf_dep_error
+
+else
+
+$(BINDIR)/$(CONFIG)/bm_callback_unary_ping_pong: $(PROTOBUF_DEP) $(BM_CALLBACK_UNARY_PING_PONG_OBJS) $(LIBDIR)/$(CONFIG)/libgrpc_benchmark.a $(LIBDIR)/$(CONFIG)/libbenchmark.a $(LIBDIR)/$(CONFIG)/libgrpc++_test_util_unsecure.a $(LIBDIR)/$(CONFIG)/libgrpc_test_util_unsecure.a $(LIBDIR)/$(CONFIG)/libgrpc++_unsecure.a $(LIBDIR)/$(CONFIG)/libgrpc_unsecure.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc++_test_config.a $(LIBDIR)/$(CONFIG)/libbm_callback_test_service_impl.a
+	$(E) "[LD]      Linking $@"
+	$(Q) mkdir -p `dirname $@`
+	$(Q) $(LDXX) $(LDFLAGS) $(BM_CALLBACK_UNARY_PING_PONG_OBJS) $(LIBDIR)/$(CONFIG)/libgrpc_benchmark.a $(LIBDIR)/$(CONFIG)/libbenchmark.a $(LIBDIR)/$(CONFIG)/libgrpc++_test_util_unsecure.a $(LIBDIR)/$(CONFIG)/libgrpc_test_util_unsecure.a $(LIBDIR)/$(CONFIG)/libgrpc++_unsecure.a $(LIBDIR)/$(CONFIG)/libgrpc_unsecure.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc++_test_config.a $(LIBDIR)/$(CONFIG)/libbm_callback_test_service_impl.a $(LDLIBSXX) $(LDLIBS_PROTOBUF) $(LDLIBS) $(LDLIBS_SECURE) $(GTEST_LIB) -o $(BINDIR)/$(CONFIG)/bm_callback_unary_ping_pong
+
+endif
+
+endif
+
+$(BM_CALLBACK_UNARY_PING_PONG_OBJS): CPPFLAGS += -Ithird_party/benchmark/include -DHAVE_POSIX_REGEX
+$(OBJDIR)/$(CONFIG)/test/cpp/microbenchmarks/bm_callback_unary_ping_pong.o:  $(LIBDIR)/$(CONFIG)/libgrpc_benchmark.a $(LIBDIR)/$(CONFIG)/libbenchmark.a $(LIBDIR)/$(CONFIG)/libgrpc++_test_util_unsecure.a $(LIBDIR)/$(CONFIG)/libgrpc_test_util_unsecure.a $(LIBDIR)/$(CONFIG)/libgrpc++_unsecure.a $(LIBDIR)/$(CONFIG)/libgrpc_unsecure.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc++_test_config.a $(LIBDIR)/$(CONFIG)/libbm_callback_test_service_impl.a
+
+deps_bm_callback_unary_ping_pong: $(BM_CALLBACK_UNARY_PING_PONG_OBJS:.o=.dep)
+
+ifneq ($(NO_SECURE),true)
+ifneq ($(NO_DEPS),true)
+-include $(BM_CALLBACK_UNARY_PING_PONG_OBJS:.o=.dep)
+endif
+endif
+
+
 BM_CHANNEL_SRC = \
     test/cpp/microbenchmarks/bm_channel.cc \
 
@@ -22284,6 +22432,7 @@ test/cpp/interop/interop_client.cc: $(OPENSSL_DEP)
 test/cpp/interop/interop_server.cc: $(OPENSSL_DEP)
 test/cpp/interop/interop_server_bootstrap.cc: $(OPENSSL_DEP)
 test/cpp/interop/server_helper.cc: $(OPENSSL_DEP)
+test/cpp/microbenchmarks/callback_test_service.cc: $(OPENSSL_DEP)
 test/cpp/microbenchmarks/helpers.cc: $(OPENSSL_DEP)
 test/cpp/naming/dns_test_util.cc: $(OPENSSL_DEP)
 test/cpp/qps/benchmark_config.cc: $(OPENSSL_DEP)
diff --git a/build.yaml b/build.yaml
index 6368db397bd..6a16596ac83 100644
--- a/build.yaml
+++ b/build.yaml
@@ -13,8 +13,8 @@ settings:
   '#09': Per-language overrides are possible with (eg) ruby_version tag here
   '#10': See the expand_version.py for all the quirks here
   core_version: 7.0.0
-  g_stands_for: gandalf
-  version: 1.21.0-dev
+  g_stands_for: gale
+  version: 1.22.0-dev
 filegroups:
 - name: alts_proto
   headers:
@@ -525,6 +525,7 @@ filegroups:
   - src/core/lib/slice/slice_hash_table.h
   - src/core/lib/slice/slice_internal.h
   - src/core/lib/slice/slice_string_helpers.h
+  - src/core/lib/slice/slice_utils.h
   - src/core/lib/slice/slice_weak_hash_table.h
   - src/core/lib/surface/api_trace.h
   - src/core/lib/surface/call.h
@@ -795,7 +796,6 @@ filegroups:
   uses:
   - grpc_base
   - grpc_client_channel
-  - grpc_resolver_dns_selection
 - name: grpc_resolver_dns_native
   src:
   - src/core/ext/filters/client_channel/resolver/dns/native/dns_resolver.cc
@@ -803,14 +803,6 @@ filegroups:
   uses:
   - grpc_base
   - grpc_client_channel
-  - grpc_resolver_dns_selection
-- name: grpc_resolver_dns_selection
-  headers:
-  - src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.h
-  src:
-  - src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.cc
-  uses:
-  - grpc_base
 - name: grpc_resolver_fake
   headers:
   - src/core/ext/filters/client_channel/resolver/fake/fake_resolver.h
@@ -1686,6 +1678,24 @@ libs:
   - grpc_test_util
   - grpc
   - gpr
+- name: bm_callback_test_service_impl
+  build: test
+  language: c++
+  headers:
+  - test/cpp/microbenchmarks/callback_test_service.h
+  src:
+  - src/proto/grpc/testing/echo.proto
+  - test/cpp/microbenchmarks/callback_test_service.cc
+  deps:
+  - grpc_benchmark
+  - benchmark
+  - grpc++_test_util_unsecure
+  - grpc_test_util_unsecure
+  - grpc++_unsecure
+  - grpc_unsecure
+  - gpr
+  - grpc++_test_config
+  defaults: benchmark
 - name: dns_test_util
   build: private
   language: c++
@@ -4052,6 +4062,52 @@ targets:
   - linux
   - posix
   uses_polling: false
+- name: bm_callback_streaming_ping_pong
+  build: test
+  language: c++
+  headers:
+  - test/cpp/microbenchmarks/callback_streaming_ping_pong.h
+  src:
+  - test/cpp/microbenchmarks/bm_callback_streaming_ping_pong.cc
+  deps:
+  - grpc_benchmark
+  - benchmark
+  - grpc++_test_util_unsecure
+  - grpc_test_util_unsecure
+  - grpc++_unsecure
+  - grpc_unsecure
+  - gpr
+  - grpc++_test_config
+  - bm_callback_test_service_impl
+  benchmark: true
+  defaults: benchmark
+  platforms:
+  - mac
+  - linux
+  - posix
+- name: bm_callback_unary_ping_pong
+  build: test
+  language: c++
+  headers:
+  - test/cpp/microbenchmarks/callback_unary_ping_pong.h
+  src:
+  - test/cpp/microbenchmarks/bm_callback_unary_ping_pong.cc
+  deps:
+  - grpc_benchmark
+  - benchmark
+  - grpc++_test_util_unsecure
+  - grpc_test_util_unsecure
+  - grpc++_unsecure
+  - grpc_unsecure
+  - gpr
+  - grpc++_test_config
+  - bm_callback_test_service_impl
+  benchmark: true
+  defaults: benchmark
+  platforms:
+  - mac
+  - linux
+  - posix
 - name: bm_channel
   build: test
   language: c++
diff --git a/config.m4 b/config.m4
index bb30be56910..4dc6a7ce34e 100644
--- a/config.m4
+++ b/config.m4
@@ -411,7 +411,6 @@ if test "$PHP_GRPC" != "no"; then
     src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_libuv.cc \
     src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_posix.cc \
     src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_windows.cc \
-    src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.cc \
     src/core/ext/filters/client_channel/resolver/dns/native/dns_resolver.cc \
     src/core/ext/filters/client_channel/resolver/sockaddr/sockaddr_resolver.cc \
     src/core/ext/filters/census/grpc_context.cc \
@@ -695,7 +694,6 @@ if test "$PHP_GRPC" != "no"; then
   PHP_ADD_BUILD_DIR($ext_builddir/src/core/ext/filters/client_channel/lb_policy/pick_first)
   PHP_ADD_BUILD_DIR($ext_builddir/src/core/ext/filters/client_channel/lb_policy/round_robin)
   PHP_ADD_BUILD_DIR($ext_builddir/src/core/ext/filters/client_channel/lb_policy/xds)
-  PHP_ADD_BUILD_DIR($ext_builddir/src/core/ext/filters/client_channel/resolver/dns)
   PHP_ADD_BUILD_DIR($ext_builddir/src/core/ext/filters/client_channel/resolver/dns/c_ares)
   PHP_ADD_BUILD_DIR($ext_builddir/src/core/ext/filters/client_channel/resolver/dns/native)
   PHP_ADD_BUILD_DIR($ext_builddir/src/core/ext/filters/client_channel/resolver/fake)
diff --git a/config.w32 b/config.w32
index c9faa8d9ac8..ec65248e0d6 100644
--- a/config.w32
+++ b/config.w32
@@ -386,7 +386,6 @@ if (PHP_GRPC != "no") {
     "src\\core\\ext\\filters\\client_channel\\resolver\\dns\\c_ares\\grpc_ares_wrapper_libuv.cc " +
     "src\\core\\ext\\filters\\client_channel\\resolver\\dns\\c_ares\\grpc_ares_wrapper_posix.cc " +
     "src\\core\\ext\\filters\\client_channel\\resolver\\dns\\c_ares\\grpc_ares_wrapper_windows.cc " +
-    "src\\core\\ext\\filters\\client_channel\\resolver\\dns\\dns_resolver_selection.cc " +
     "src\\core\\ext\\filters\\client_channel\\resolver\\dns\\native\\dns_resolver.cc " +
     "src\\core\\ext\\filters\\client_channel\\resolver\\sockaddr\\sockaddr_resolver.cc " +
     "src\\core\\ext\\filters\\census\\grpc_context.cc " +
diff --git a/doc/g_stands_for.md b/doc/g_stands_for.md
index b926db191de..90202b1b880 100644
--- a/doc/g_stands_for.md
+++ b/doc/g_stands_for.md
@@ -20,4 +20,5 @@
 - 1.18 'g' stands for ['goose'](https://github.com/grpc/grpc/tree/v1.18.x)
 - 1.19 'g' stands for ['gold'](https://github.com/grpc/grpc/tree/v1.19.x)
 - 1.20 'g' stands for ['godric'](https://github.com/grpc/grpc/tree/v1.20.x)
-- 1.21 'g' stands for ['gandalf'](https://github.com/grpc/grpc/tree/master)
+- 1.21 'g' stands for ['gandalf'](https://github.com/grpc/grpc/tree/v1.21.x)
+- 1.22 'g' stands for ['gale'](https://github.com/grpc/grpc/tree/master)
diff --git a/gRPC-C++.podspec b/gRPC-C++.podspec
index 86c5f211f27..a4b38bcbdc0 100644
--- a/gRPC-C++.podspec
+++ b/gRPC-C++.podspec
@@ -23,7 +23,7 @@
 Pod::Spec.new do |s|
   s.name     = 'gRPC-C++'
   # TODO (mxyan): use version that match gRPC version when pod is stabilized
-  # version = '1.21.0-dev'
+  # version = '1.22.0-dev'
   version = '0.0.8-dev'
   s.version  = version
   s.summary  = 'gRPC C++ library'
@@ -31,7 +31,7 @@ Pod::Spec.new do |s|
   s.license  = 'Apache License, Version 2.0'
   s.authors  = { 'The gRPC contributors' => 'grpc-packages@google.com' }
 
-  grpc_version = '1.21.0-dev'
+  grpc_version = '1.22.0-dev'
 
   s.source = {
     :git => 'https://github.com/grpc/grpc.git',
@@ -518,6 +518,7 @@ Pod::Spec.new do |s|
                       'src/core/lib/slice/slice_hash_table.h',
                       'src/core/lib/slice/slice_internal.h',
                       'src/core/lib/slice/slice_string_helpers.h',
+                      'src/core/lib/slice/slice_utils.h',
                       'src/core/lib/slice/slice_weak_hash_table.h',
                       'src/core/lib/surface/api_trace.h',
                       'src/core/lib/surface/call.h',
@@ -562,7 +563,6 @@ Pod::Spec.new do |s|
                       'src/core/ext/filters/client_channel/lb_policy/subchannel_list.h',
                       'src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver.h',
                       'src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.h',
-                      'src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.h',
                       'src/core/ext/filters/max_age/max_age_filter.h',
                       'src/core/ext/filters/message_size/message_size_filter.h',
                       'src/core/ext/filters/http/client_authority_filter.h',
@@ -720,6 +720,7 @@ Pod::Spec.new do |s|
                               'src/core/lib/slice/slice_hash_table.h',
                               'src/core/lib/slice/slice_internal.h',
                               'src/core/lib/slice/slice_string_helpers.h',
+                              'src/core/lib/slice/slice_utils.h',
                               'src/core/lib/slice/slice_weak_hash_table.h',
                               'src/core/lib/surface/api_trace.h',
                               'src/core/lib/surface/call.h',
diff --git a/gRPC-Core.podspec b/gRPC-Core.podspec
index 069c319ec0b..682b7d80277 100644
--- a/gRPC-Core.podspec
+++ b/gRPC-Core.podspec
@@ -22,7 +22,7 @@
 
 Pod::Spec.new do |s|
   s.name     = 'gRPC-Core'
-  version = '1.21.0-dev'
+  version = '1.22.0-dev'
   s.version  = version
   s.summary  = 'Core cross-platform gRPC library, written in C'
   s.homepage = 'https://grpc.io'
@@ -494,6 +494,7 @@ Pod::Spec.new do |s|
                       'src/core/lib/slice/slice_hash_table.h',
                       'src/core/lib/slice/slice_internal.h',
                       'src/core/lib/slice/slice_string_helpers.h',
+                      'src/core/lib/slice/slice_utils.h',
                       'src/core/lib/slice/slice_weak_hash_table.h',
                       'src/core/lib/surface/api_trace.h',
                       'src/core/lib/surface/call.h',
@@ -538,7 +539,6 @@ Pod::Spec.new do |s|
                       'src/core/ext/filters/client_channel/lb_policy/subchannel_list.h',
                       'src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver.h',
                       'src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.h',
-                      'src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.h',
                       'src/core/ext/filters/max_age/max_age_filter.h',
                       'src/core/ext/filters/message_size/message_size_filter.h',
                       'src/core/ext/filters/http/client_authority_filter.h',
@@ -868,7 +868,6 @@ Pod::Spec.new do |s|
                       'src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_libuv.cc',
                       'src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_posix.cc',
                       'src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_windows.cc',
-                      'src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.cc',
                       'src/core/ext/filters/client_channel/resolver/dns/native/dns_resolver.cc',
                       'src/core/ext/filters/client_channel/resolver/sockaddr/sockaddr_resolver.cc',
                       'src/core/ext/filters/census/grpc_context.cc',
@@ -1145,6 +1144,7 @@ Pod::Spec.new do |s|
                               'src/core/lib/slice/slice_hash_table.h',
                               'src/core/lib/slice/slice_internal.h',
                               'src/core/lib/slice/slice_string_helpers.h',
+                              'src/core/lib/slice/slice_utils.h',
                               'src/core/lib/slice/slice_weak_hash_table.h',
                               'src/core/lib/surface/api_trace.h',
                               'src/core/lib/surface/call.h',
@@ -1189,7 +1189,6 @@ Pod::Spec.new do |s|
                               'src/core/ext/filters/client_channel/lb_policy/subchannel_list.h',
                               'src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver.h',
                               'src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.h',
-                              'src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.h',
                               'src/core/ext/filters/max_age/max_age_filter.h',
                               'src/core/ext/filters/message_size/message_size_filter.h',
                               'src/core/ext/filters/http/client_authority_filter.h',
diff --git a/gRPC-ProtoRPC.podspec b/gRPC-ProtoRPC.podspec
index 0e905bd97bd..1cac59c6cc4 100644
--- a/gRPC-ProtoRPC.podspec
+++ b/gRPC-ProtoRPC.podspec
@@ -21,7 +21,7 @@
 
 Pod::Spec.new do |s|
   s.name     = 'gRPC-ProtoRPC'
-  version = '1.21.0-dev'
+  version = '1.22.0-dev'
   s.version  = version
   s.summary  = 'RPC library for Protocol Buffers, based on gRPC'
   s.homepage = 'https://grpc.io'
diff --git a/gRPC-RxLibrary.podspec b/gRPC-RxLibrary.podspec
index df86ef7ed34..6f033ea71b7 100644
--- a/gRPC-RxLibrary.podspec
+++ b/gRPC-RxLibrary.podspec
@@ -21,7 +21,7 @@
 
 Pod::Spec.new do |s|
   s.name     = 'gRPC-RxLibrary'
-  version = '1.21.0-dev'
+  version = '1.22.0-dev'
   s.version  = version
   s.summary  = 'Reactive Extensions library for iOS/OSX.'
   s.homepage = 'https://grpc.io'
diff --git a/gRPC.podspec b/gRPC.podspec
index b3c7a55a2e1..e9c3fd7bee0 100644
--- a/gRPC.podspec
+++ b/gRPC.podspec
@@ -20,7 +20,7 @@
 
 Pod::Spec.new do |s|
   s.name     = 'gRPC'
-  version = '1.21.0-dev'
+  version = '1.22.0-dev'
   s.version  = version
   s.summary  = 'gRPC client library for iOS/OSX'
   s.homepage = 'https://grpc.io'
diff --git a/grpc.gemspec b/grpc.gemspec
index 5a34687b4d9..36b325f8f0d 100644
--- a/grpc.gemspec
+++ b/grpc.gemspec
@@ -428,6 +428,7 @@ Gem::Specification.new do |s|
   s.files += %w( src/core/lib/slice/slice_hash_table.h )
   s.files += %w( src/core/lib/slice/slice_internal.h )
   s.files += %w( src/core/lib/slice/slice_string_helpers.h )
+  s.files += %w( src/core/lib/slice/slice_utils.h )
   s.files += %w( src/core/lib/slice/slice_weak_hash_table.h )
   s.files += %w( src/core/lib/surface/api_trace.h )
   s.files += %w( src/core/lib/surface/call.h )
@@ -472,7 +473,6 @@ Gem::Specification.new do |s|
   s.files += %w( src/core/ext/filters/client_channel/lb_policy/subchannel_list.h )
   s.files += %w( src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver.h )
   s.files += %w( src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.h )
-  s.files += %w( src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.h )
   s.files += %w( src/core/ext/filters/max_age/max_age_filter.h )
   s.files += %w( src/core/ext/filters/message_size/message_size_filter.h )
   s.files += %w( src/core/ext/filters/http/client_authority_filter.h )
@@ -805,7 +805,6 @@ Gem::Specification.new do |s|
   s.files += %w( src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_libuv.cc )
   s.files += %w( src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_posix.cc )
   s.files += %w( src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_windows.cc )
-  s.files += %w( src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.cc )
   s.files += %w( src/core/ext/filters/client_channel/resolver/dns/native/dns_resolver.cc )
   s.files += %w( src/core/ext/filters/client_channel/resolver/sockaddr/sockaddr_resolver.cc )
   s.files += %w( src/core/ext/filters/census/grpc_context.cc )
diff --git a/grpc.gyp b/grpc.gyp
index 1cc6e46b4be..39eab073107 100644
--- a/grpc.gyp
+++ b/grpc.gyp
@@ -593,7 +593,6 @@
         'src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_libuv.cc',
         'src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_posix.cc',
         'src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_windows.cc',
-        'src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.cc',
         'src/core/ext/filters/client_channel/resolver/dns/native/dns_resolver.cc',
         'src/core/ext/filters/client_channel/resolver/sockaddr/sockaddr_resolver.cc',
         'src/core/ext/filters/census/grpc_context.cc',
@@ -1353,7 +1352,6 @@
         'src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_libuv.cc',
         'src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_posix.cc',
         'src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_windows.cc',
-        'src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.cc',
         'src/core/ext/filters/client_channel/resolver/dns/native/dns_resolver.cc',
         'src/core/ext/filters/client_channel/resolver/sockaddr/sockaddr_resolver.cc',
         'src/core/ext/filters/client_channel/resolver/fake/fake_resolver.cc',
@@ -1405,6 +1403,24 @@
         'test/core/util/test_tcp_server.cc',
       ],
     },
+    {
+      'target_name': 'bm_callback_test_service_impl',
+      'type': 'static_library',
+      'dependencies': [
+        'grpc_benchmark',
+        'benchmark',
+        'grpc++_test_util_unsecure',
+        'grpc_test_util_unsecure',
+        'grpc++_unsecure',
+        'grpc_unsecure',
+        'gpr',
+        'grpc++_test_config',
+      ],
+      'sources': [
+        'src/proto/grpc/testing/echo.proto',
+        'test/cpp/microbenchmarks/callback_test_service.cc',
+      ],
+    },
     {
       'target_name': 'dns_test_util',
       'type': 'static_library',
diff --git a/include/grpc/grpc_security.h b/include/grpc/grpc_security.h
index 53189097b9b..ebdf86b7d50 100644
--- a/include/grpc/grpc_security.h
+++ b/include/grpc/grpc_security.h
@@ -641,7 +641,7 @@ typedef struct grpc_tls_credentials_options grpc_tls_credentials_options;
 
 /** Create an empty TLS credentials options. It is used for
  *  experimental purpose for now and subject to change. */
-GRPCAPI grpc_tls_credentials_options* grpc_tls_credentials_options_create();
+GRPCAPI grpc_tls_credentials_options* grpc_tls_credentials_options_create(void);
 
 /** Set grpc_ssl_client_certificate_request_type field in credentials options
     with the provided type. options should not be NULL.
@@ -683,7 +683,8 @@ GRPCAPI int grpc_tls_credentials_options_set_server_authorization_check_config(
 
 /** Create an empty grpc_tls_key_materials_config instance.
  *  It is used for experimental purpose for now and subject to change. */
-GRPCAPI grpc_tls_key_materials_config* grpc_tls_key_materials_config_create();
+GRPCAPI grpc_tls_key_materials_config* grpc_tls_key_materials_config_create(
+    void);
 
 /** Set grpc_tls_key_materials_config instance with provided a TLS certificate.
     config will take the ownership of pem_root_certs and pem_key_cert_pairs.
diff --git a/include/grpcpp/server_impl.h b/include/grpcpp/server_impl.h
index 2a53265bb55..9d02af8d11f 100644
--- a/include/grpcpp/server_impl.h
+++ b/include/grpcpp/server_impl.h
@@ -200,6 +200,18 @@ class Server : public grpc::ServerInterface, private grpc::GrpcLibraryCodegen {
 
   grpc_server* server() override { return server_; }
 
+ protected:
+  /// NOTE: This method is not part of the public API for this class.
+  void set_health_check_service(
+      std::unique_ptr<grpc::HealthCheckServiceInterface> service) {
+    health_check_service_ = std::move(service);
+  }
+
+  /// NOTE: This method is not part of the public API for this class.
+  bool health_check_service_disabled() const {
+    return health_check_service_disabled_;
+  }
+
  private:
   std::vector<
       std::unique_ptr<grpc::experimental::ServerInterceptorFactoryInterface>>*
diff --git a/package.xml b/package.xml
index 201b4a3e951..da12917dbee 100644
--- a/package.xml
+++ b/package.xml
@@ -13,8 +13,8 @@
  <date>2018-01-19</date>
  <time>16:06:07</time>
  <version>
-  <release>1.21.0dev</release>
-  <api>1.21.0dev</api>
+  <release>1.22.0dev</release>
+  <api>1.22.0dev</api>
  </version>
  <stability>
   <release>beta</release>
@@ -433,6 +433,7 @@
     <file baseinstalldir="/" name="src/core/lib/slice/slice_hash_table.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/slice/slice_internal.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/slice/slice_string_helpers.h" role="src" />
+    <file baseinstalldir="/" name="src/core/lib/slice/slice_utils.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/slice/slice_weak_hash_table.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/surface/api_trace.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/surface/call.h" role="src" />
@@ -477,7 +478,6 @@
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/lb_policy/subchannel_list.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.h" role="src" />
-    <file baseinstalldir="/" name="src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/max_age/max_age_filter.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/message_size/message_size_filter.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/http/client_authority_filter.h" role="src" />
@@ -810,7 +810,6 @@
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_libuv.cc" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_posix.cc" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_windows.cc" role="src" />
-    <file baseinstalldir="/" name="src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.cc" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/resolver/dns/native/dns_resolver.cc" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/resolver/sockaddr/sockaddr_resolver.cc" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/census/grpc_context.cc" role="src" />
diff --git a/src/android/test/interop/app/src/main/cpp/grpc-interop.cc b/src/android/test/interop/app/src/main/cpp/grpc-interop.cc
index b5075529be2..07834250d22 100644
--- a/src/android/test/interop/app/src/main/cpp/grpc-interop.cc
+++ b/src/android/test/interop/app/src/main/cpp/grpc-interop.cc
@@ -18,8 +18,8 @@
 
 #include <grpcpp/grpcpp.h>
 #include <jni.h>
+#include <src/core/lib/gpr/env.h>
 
-#include "src/core/lib/security/security_connector/ssl_utils.h"
 #include "test/cpp/interop/interop_client.h"
 
 extern "C" JNIEXPORT void JNICALL
@@ -28,7 +28,7 @@ Java_io_grpc_interop_cpp_InteropActivity_configureSslRoots(JNIEnv* env,
                                                            jstring path_raw) {
   const char* path = env->GetStringUTFChars(path_raw, (jboolean*)0);
 
-  GPR_GLOBAL_CONFIG_SET(grpc_default_ssl_roots_file_path, path);
+  gpr_setenv("GRPC_DEFAULT_SSL_ROOTS_FILE_PATH", path);
 }
 
 std::shared_ptr<grpc::testing::InteropClient> GetClient(const char* host,
@@ -45,7 +45,7 @@ std::shared_ptr<grpc::testing::InteropClient> GetClient(const char* host,
     credentials = grpc::InsecureChannelCredentials();
   }
 
-  grpc::testing::ChannelCreationFunc channel_creation_func =
+  grpc::testing::ChannelCreationFunc channel_creation_func = 
       std::bind(grpc::CreateChannel, host_port, credentials);
   return std::shared_ptr<grpc::testing::InteropClient>(
       new grpc::testing::InteropClient(channel_creation_func, true, false));
diff --git a/src/core/ext/filters/client_channel/backup_poller.cc b/src/core/ext/filters/client_channel/backup_poller.cc
index dd761694414..a2d45c04026 100644
--- a/src/core/ext/filters/client_channel/backup_poller.cc
+++ b/src/core/ext/filters/client_channel/backup_poller.cc
@@ -56,14 +56,9 @@ static backup_poller* g_poller = nullptr;  // guarded by g_poller_mu
 // treated as const.
 static int g_poll_interval_ms = DEFAULT_POLL_INTERVAL_MS;
 
-GPR_GLOBAL_CONFIG_DEFINE_INT32(
-    grpc_client_channel_backup_poll_interval_ms, DEFAULT_POLL_INTERVAL_MS,
-    "Declares the interval in ms between two backup polls on client channels. "
-    "These polls are run in the timer thread so that gRPC can process "
-    "connection failures while there is no active polling thread. "
-    "They help reconnect disconnected client channels (mostly due to "
-    "idleness), so that the next RPC on this channel won't fail. Set to 0 to "
-    "turn off the backup polls.");
+GPR_GLOBAL_CONFIG_DEFINE_INT32(grpc_client_channel_backup_poll_interval_ms,
+                               DEFAULT_POLL_INTERVAL_MS,
+                               "Client channel backup poll interval (ms)");
 
 static void init_globals() {
   gpr_mu_init(&g_poller_mu);
diff --git a/src/core/ext/filters/client_channel/client_channel.cc b/src/core/ext/filters/client_channel/client_channel.cc
index f774c985c30..cc4bfdded13 100644
--- a/src/core/ext/filters/client_channel/client_channel.cc
+++ b/src/core/ext/filters/client_channel/client_channel.cc
@@ -222,7 +222,7 @@ class ChannelData {
   ~ChannelData();
 
   static bool ProcessResolverResultLocked(
-      void* arg, const Resolver::Result& result, const char** lb_policy_name,
+      void* arg, Resolver::Result* result, const char** lb_policy_name,
       RefCountedPtr<ParsedLoadBalancingConfig>* lb_policy_config,
       grpc_error** service_config_error);
 
@@ -271,7 +271,6 @@ class ChannelData {
   OrphanablePtr<LoadBalancingPolicy> resolving_lb_policy_;
   grpc_connectivity_state_tracker state_tracker_;
   ExternalConnectivityWatcher::WatcherList external_connectivity_watcher_list_;
-  UniquePtr<char> health_check_service_name_;
   RefCountedPtr<ServiceConfig> saved_service_config_;
   bool received_first_resolver_result_ = false;
 
@@ -951,18 +950,10 @@ class ChannelData::ClientChannelControlHelper
   }
 
   Subchannel* CreateSubchannel(const grpc_channel_args& args) override {
-    grpc_arg args_to_add[2];
-    int num_args_to_add = 0;
-    if (chand_->health_check_service_name_ != nullptr) {
-      args_to_add[0] = grpc_channel_arg_string_create(
-          const_cast<char*>("grpc.temp.health_check"),
-          const_cast<char*>(chand_->health_check_service_name_.get()));
-      num_args_to_add++;
-    }
-    args_to_add[num_args_to_add++] = SubchannelPoolInterface::CreateChannelArg(
+    grpc_arg arg = SubchannelPoolInterface::CreateChannelArg(
         chand_->subchannel_pool_.get());
     grpc_channel_args* new_args =
-        grpc_channel_args_copy_and_add(&args, args_to_add, num_args_to_add);
+        grpc_channel_args_copy_and_add(&args, &arg, 1);
     Subchannel* subchannel =
         chand_->client_channel_factory_->CreateSubchannel(new_args);
     grpc_channel_args_destroy(new_args);
@@ -1078,8 +1069,6 @@ ChannelData::ChannelData(grpc_channel_element_args* args, grpc_error** error)
   // Get default service config
   const char* service_config_json = grpc_channel_arg_get_string(
       grpc_channel_args_find(args->channel_args, GRPC_ARG_SERVICE_CONFIG));
-  // TODO(yashkt): Make sure we set the channel in TRANSIENT_FAILURE on an
-  // invalid default service config
   if (service_config_json != nullptr) {
     *error = GRPC_ERROR_NONE;
     default_service_config_ = ServiceConfig::Create(service_config_json, error);
@@ -1201,14 +1190,14 @@ void ChannelData::ProcessLbPolicy(
 // Synchronous callback from ResolvingLoadBalancingPolicy to process a
 // resolver result update.
 bool ChannelData::ProcessResolverResultLocked(
-    void* arg, const Resolver::Result& result, const char** lb_policy_name,
+    void* arg, Resolver::Result* result, const char** lb_policy_name,
     RefCountedPtr<ParsedLoadBalancingConfig>* lb_policy_config,
     grpc_error** service_config_error) {
   ChannelData* chand = static_cast<ChannelData*>(arg);
   RefCountedPtr<ServiceConfig> service_config;
   // If resolver did not return a service config or returned an invalid service
   // config, we need a fallback service config.
-  if (result.service_config_error != GRPC_ERROR_NONE) {
+  if (result->service_config_error != GRPC_ERROR_NONE) {
     // If the service config was invalid, then fallback to the saved service
     // config. If there is no saved config either, use the default service
     // config.
@@ -1229,7 +1218,7 @@ bool ChannelData::ProcessResolverResultLocked(
       }
       service_config = chand->default_service_config_;
     }
-  } else if (result.service_config == nullptr) {
+  } else if (result->service_config == nullptr) {
     if (chand->default_service_config_ != nullptr) {
       if (GRPC_TRACE_FLAG_ENABLED(grpc_client_channel_routing_trace)) {
         gpr_log(GPR_INFO,
@@ -1240,15 +1229,15 @@ bool ChannelData::ProcessResolverResultLocked(
       service_config = chand->default_service_config_;
     }
   } else {
-    service_config = result.service_config;
+    service_config = result->service_config;
   }
-  *service_config_error = GRPC_ERROR_REF(result.service_config_error);
+  *service_config_error = GRPC_ERROR_REF(result->service_config_error);
   if (service_config == nullptr &&
-      result.service_config_error != GRPC_ERROR_NONE) {
+      result->service_config_error != GRPC_ERROR_NONE) {
     return false;
   }
-  UniquePtr<char> service_config_json;
   // Process service config.
+  UniquePtr<char> service_config_json;
   const internal::ClientChannelGlobalParsedObject* parsed_service_config =
       nullptr;
   if (service_config != nullptr) {
@@ -1257,6 +1246,20 @@ bool ChannelData::ProcessResolverResultLocked(
             service_config->GetParsedGlobalServiceConfigObject(
                 internal::ClientChannelServiceConfigParser::ParserIndex()));
   }
+  // TODO(roth): Eliminate this hack as part of hiding health check
+  // service name from LB policy API.  As part of this, change the API
+  // for this function to pass in result as a const reference.
+  if (parsed_service_config != nullptr &&
+      parsed_service_config->health_check_service_name() != nullptr) {
+    grpc_arg new_arg = grpc_channel_arg_string_create(
+        const_cast<char*>("grpc.temp.health_check"),
+        const_cast<char*>(parsed_service_config->health_check_service_name()));
+    grpc_channel_args* new_args =
+        grpc_channel_args_copy_and_add(result->args, &new_arg, 1);
+    grpc_channel_args_destroy(result->args);
+    result->args = new_args;
+  }
+  // Check if the config has changed.
   const bool service_config_changed =
       ((service_config == nullptr) !=
        (chand->saved_service_config_ == nullptr)) ||
@@ -1273,12 +1276,6 @@ bool ChannelData::ProcessResolverResultLocked(
               chand, service_config_json.get());
     }
     chand->saved_service_config_ = std::move(service_config);
-    if (parsed_service_config != nullptr) {
-      chand->health_check_service_name_.reset(
-          gpr_strdup(parsed_service_config->health_check_service_name()));
-    } else {
-      chand->health_check_service_name_.reset();
-    }
   }
   // We want to set the service config at least once. This should not really be
   // needed, but we are doing it as a defensive approach. This can be removed,
@@ -1296,7 +1293,7 @@ bool ChannelData::ProcessResolverResultLocked(
                              chand->saved_service_config_);
   }
   UniquePtr<char> processed_lb_policy_name;
-  chand->ProcessLbPolicy(result, parsed_service_config,
+  chand->ProcessLbPolicy(*result, parsed_service_config,
                          &processed_lb_policy_name, lb_policy_config);
   // Swap out the data used by GetChannelInfo().
   {
diff --git a/src/core/ext/filters/client_channel/client_channel_channelz.cc b/src/core/ext/filters/client_channel/client_channel_channelz.cc
index a7a47e9eb10..de61819ef54 100644
--- a/src/core/ext/filters/client_channel/client_channel_channelz.cc
+++ b/src/core/ext/filters/client_channel/client_channel_channelz.cc
@@ -127,7 +127,9 @@ void SubchannelNode::PopulateConnectivityState(grpc_json* json) {
   if (subchannel_ == nullptr) {
     state = GRPC_CHANNEL_SHUTDOWN;
   } else {
-    state = subchannel_->CheckConnectivity(true /* inhibit_health_checking */);
+    state = subchannel_->CheckConnectivityState(
+        nullptr /* health_check_service_name */,
+        nullptr /* connected_subchannel */);
   }
   json = grpc_json_create_child(nullptr, json, "state", nullptr,
                                 GRPC_JSON_OBJECT, false);
diff --git a/src/core/ext/filters/client_channel/health/health_check_client.cc b/src/core/ext/filters/client_channel/health/health_check_client.cc
index bfac773899d..faa2ba5b3b1 100644
--- a/src/core/ext/filters/client_channel/health/health_check_client.cc
+++ b/src/core/ext/filters/client_channel/health/health_check_client.cc
@@ -323,6 +323,11 @@ void HealthCheckClient::CallState::StartCall() {
   grpc_error* error = GRPC_ERROR_NONE;
   call_ = health_check_client_->connected_subchannel_->CreateCall(args, &error)
               .release();
+  // Register after-destruction callback.
+  GRPC_CLOSURE_INIT(&after_call_stack_destruction_, AfterCallStackDestruction,
+                    this, grpc_schedule_on_exec_ctx);
+  call_->SetAfterCallStackDestroy(&after_call_stack_destruction_);
+  // Check if creation failed.
   if (error != GRPC_ERROR_NONE) {
     gpr_log(GPR_ERROR,
             "HealthCheckClient %p CallState %p: error creating health "
@@ -338,10 +343,6 @@ void HealthCheckClient::CallState::StartCall() {
         GRPC_ERROR_NONE);
     return;
   }
-  // Register after-destruction callback.
-  GRPC_CLOSURE_INIT(&after_call_stack_destruction_, AfterCallStackDestruction,
-                    this, grpc_schedule_on_exec_ctx);
-  call_->SetAfterCallStackDestroy(&after_call_stack_destruction_);
   // Initialize payload and batch.
   payload_.context = context_;
   batch_.payload = &payload_;
diff --git a/src/core/ext/filters/client_channel/http_connect_handshaker.cc b/src/core/ext/filters/client_channel/http_connect_handshaker.cc
index 95366b57386..90a79843458 100644
--- a/src/core/ext/filters/client_channel/http_connect_handshaker.cc
+++ b/src/core/ext/filters/client_channel/http_connect_handshaker.cc
@@ -31,6 +31,7 @@
 #include "src/core/ext/filters/client_channel/resolver_registry.h"
 #include "src/core/lib/channel/channel_args.h"
 #include "src/core/lib/channel/handshaker_registry.h"
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/string.h"
 #include "src/core/lib/gprpp/sync.h"
 #include "src/core/lib/http/format_request.h"
diff --git a/src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc b/src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc
index bc2f6e5efd6..199e973e72c 100644
--- a/src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc
@@ -68,9 +68,8 @@ class PickFirst : public LoadBalancingPolicy {
     PickFirstSubchannelData(
         SubchannelList<PickFirstSubchannelList, PickFirstSubchannelData>*
             subchannel_list,
-        const ServerAddress& address, Subchannel* subchannel,
-        grpc_combiner* combiner)
-        : SubchannelData(subchannel_list, address, subchannel, combiner) {}
+        const ServerAddress& address, Subchannel* subchannel)
+        : SubchannelData(subchannel_list, address, subchannel) {}
 
     void ProcessConnectivityChangeLocked(
         grpc_connectivity_state connectivity_state) override;
@@ -312,6 +311,7 @@ void PickFirst::UpdateLocked(UpdateArgs args) {
       // here, since we've already checked the initial connectivity
       // state of all subchannels above.
       subchannel_list_->subchannel(0)->StartConnectivityWatchLocked();
+      subchannel_list_->subchannel(0)->subchannel()->AttemptToConnect();
     }
   } else {
     // We do have a selected subchannel (which means it's READY), so keep
@@ -334,6 +334,9 @@ void PickFirst::UpdateLocked(UpdateArgs args) {
       // state of all subchannels above.
       latest_pending_subchannel_list_->subchannel(0)
           ->StartConnectivityWatchLocked();
+      latest_pending_subchannel_list_->subchannel(0)
+          ->subchannel()
+          ->AttemptToConnect();
     }
   }
 }
@@ -366,7 +369,8 @@ void PickFirst::PickFirstSubchannelData::ProcessConnectivityChangeLocked(
                 p->subchannel_list_.get());
       }
       p->selected_ = nullptr;
-      StopConnectivityWatchLocked();
+      CancelConnectivityWatchLocked(
+          "selected subchannel failed; switching to pending update");
       p->subchannel_list_ = std::move(p->latest_pending_subchannel_list_);
       // Set our state to that of the pending subchannel list.
       if (p->subchannel_list_->in_transient_failure()) {
@@ -391,7 +395,7 @@ void PickFirst::PickFirstSubchannelData::ProcessConnectivityChangeLocked(
         p->idle_ = true;
         p->channel_control_helper()->RequestReresolution();
         p->selected_ = nullptr;
-        StopConnectivityWatchLocked();
+        CancelConnectivityWatchLocked("selected subchannel failed; going IDLE");
         p->channel_control_helper()->UpdateState(
             GRPC_CHANNEL_IDLE,
             UniquePtr<SubchannelPicker>(New<QueuePicker>(p->Ref())));
@@ -408,8 +412,6 @@ void PickFirst::PickFirstSubchannelData::ProcessConnectivityChangeLocked(
               connectivity_state,
               UniquePtr<SubchannelPicker>(New<QueuePicker>(p->Ref())));
         }
-        // Renew notification.
-        RenewConnectivityWatchLocked();
       }
     }
     return;
@@ -426,13 +428,11 @@ void PickFirst::PickFirstSubchannelData::ProcessConnectivityChangeLocked(
   subchannel_list()->set_in_transient_failure(false);
   switch (connectivity_state) {
     case GRPC_CHANNEL_READY: {
-      // Renew notification.
-      RenewConnectivityWatchLocked();
       ProcessUnselectedReadyLocked();
       break;
     }
     case GRPC_CHANNEL_TRANSIENT_FAILURE: {
-      StopConnectivityWatchLocked();
+      CancelConnectivityWatchLocked("connection attempt failed");
       PickFirstSubchannelData* sd = this;
       size_t next_index =
           (sd->Index() + 1) % subchannel_list()->num_subchannels();
@@ -468,8 +468,6 @@ void PickFirst::PickFirstSubchannelData::ProcessConnectivityChangeLocked(
             GRPC_CHANNEL_CONNECTING,
             UniquePtr<SubchannelPicker>(New<QueuePicker>(p->Ref())));
       }
-      // Renew notification.
-      RenewConnectivityWatchLocked();
       break;
     }
     case GRPC_CHANNEL_SHUTDOWN:
@@ -521,8 +519,11 @@ void PickFirst::PickFirstSubchannelData::
   // If current state is READY, select the subchannel now, since we started
   // watching from this state and will not get a notification of it
   // transitioning into this state.
-  if (p->selected_ != this && current_state == GRPC_CHANNEL_READY) {
-    ProcessUnselectedReadyLocked();
+  // If the current state is not READY, attempt to connect.
+  if (current_state == GRPC_CHANNEL_READY) {
+    if (p->selected_ != this) ProcessUnselectedReadyLocked();
+  } else {
+    subchannel()->AttemptToConnect();
   }
 }
 
diff --git a/src/core/ext/filters/client_channel/lb_policy/round_robin/round_robin.cc b/src/core/ext/filters/client_channel/lb_policy/round_robin/round_robin.cc
index 6d603913d82..1693032ea24 100644
--- a/src/core/ext/filters/client_channel/lb_policy/round_robin/round_robin.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/round_robin/round_robin.cc
@@ -83,9 +83,8 @@ class RoundRobin : public LoadBalancingPolicy {
     RoundRobinSubchannelData(
         SubchannelList<RoundRobinSubchannelList, RoundRobinSubchannelData>*
             subchannel_list,
-        const ServerAddress& address, Subchannel* subchannel,
-        grpc_combiner* combiner)
-        : SubchannelData(subchannel_list, address, subchannel, combiner) {}
+        const ServerAddress& address, Subchannel* subchannel)
+        : SubchannelData(subchannel_list, address, subchannel) {}
 
     grpc_connectivity_state connectivity_state() const {
       return last_connectivity_state_;
@@ -320,6 +319,7 @@ void RoundRobin::RoundRobinSubchannelList::StartWatchingLocked() {
   for (size_t i = 0; i < num_subchannels(); i++) {
     if (subchannel(i)->subchannel() != nullptr) {
       subchannel(i)->StartConnectivityWatchLocked();
+      subchannel(i)->subchannel()->AttemptToConnect();
     }
   }
   // Now set the LB policy's state based on the subchannels' states.
@@ -448,6 +448,7 @@ void RoundRobin::RoundRobinSubchannelData::ProcessConnectivityChangeLocked(
   // Otherwise, if the subchannel was already in state TRANSIENT_FAILURE
   // when the subchannel list was created, we'd wind up in a constant
   // loop of re-resolution.
+  // Also attempt to reconnect.
   if (connectivity_state == GRPC_CHANNEL_TRANSIENT_FAILURE) {
     if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_round_robin_trace)) {
       gpr_log(GPR_INFO,
@@ -456,9 +457,8 @@ void RoundRobin::RoundRobinSubchannelData::ProcessConnectivityChangeLocked(
               p, subchannel());
     }
     p->channel_control_helper()->RequestReresolution();
+    subchannel()->AttemptToConnect();
   }
-  // Renew connectivity watch.
-  RenewConnectivityWatchLocked();
   // Update state counters.
   UpdateConnectivityStateLocked(connectivity_state);
   // Update overall state and renew notification.
diff --git a/src/core/ext/filters/client_channel/lb_policy/subchannel_list.h b/src/core/ext/filters/client_channel/lb_policy/subchannel_list.h
index 4c48045f978..93b4bbd369a 100644
--- a/src/core/ext/filters/client_channel/lb_policy/subchannel_list.h
+++ b/src/core/ext/filters/client_channel/lb_policy/subchannel_list.h
@@ -98,15 +98,13 @@ class SubchannelData {
 
   // Synchronously checks the subchannel's connectivity state.
   // Must not be called while there is a connectivity notification
-  // pending (i.e., between calling StartConnectivityWatchLocked() or
-  // RenewConnectivityWatchLocked() and the resulting invocation of
-  // ProcessConnectivityChangeLocked()).
+  // pending (i.e., between calling StartConnectivityWatchLocked() and
+  // calling CancelConnectivityWatchLocked()).
   grpc_connectivity_state CheckConnectivityStateLocked() {
-    GPR_ASSERT(!connectivity_notification_pending_);
-    pending_connectivity_state_unsafe_ = subchannel()->CheckConnectivity(
-        subchannel_list_->inhibit_health_checking());
-    UpdateConnectedSubchannelLocked();
-    return pending_connectivity_state_unsafe_;
+    GPR_ASSERT(pending_watcher_ == nullptr);
+    connectivity_state_ = subchannel()->CheckConnectivityState(
+        subchannel_list_->health_check_service_name(), &connected_subchannel_);
+    return connectivity_state_;
   }
 
   // Resets the connection backoff.
@@ -115,23 +113,11 @@ class SubchannelData {
   void ResetBackoffLocked();
 
   // Starts watching the connectivity state of the subchannel.
-  // ProcessConnectivityChangeLocked() will be called when the
+  // ProcessConnectivityChangeLocked() will be called whenever the
   // connectivity state changes.
   void StartConnectivityWatchLocked();
 
-  // Renews watching the connectivity state of the subchannel.
-  void RenewConnectivityWatchLocked();
-
-  // Stops watching the connectivity state of the subchannel.
-  void StopConnectivityWatchLocked();
-
   // Cancels watching the connectivity state of the subchannel.
-  // Must be called only while there is a connectivity notification
-  // pending (i.e., between calling StartConnectivityWatchLocked() or
-  // RenewConnectivityWatchLocked() and the resulting invocation of
-  // ProcessConnectivityChangeLocked()).
-  // From within ProcessConnectivityChangeLocked(), use
-  // StopConnectivityWatchLocked() instead.
   void CancelConnectivityWatchLocked(const char* reason);
 
   // Cancels any pending connectivity watch and unrefs the subchannel.
@@ -142,44 +128,80 @@ class SubchannelData {
  protected:
   SubchannelData(
       SubchannelList<SubchannelListType, SubchannelDataType>* subchannel_list,
-      const ServerAddress& address, Subchannel* subchannel,
-      grpc_combiner* combiner);
+      const ServerAddress& address, Subchannel* subchannel);
 
   virtual ~SubchannelData();
 
-  // After StartConnectivityWatchLocked() or RenewConnectivityWatchLocked()
-  // is called, this method will be invoked when the subchannel's connectivity
-  // state changes.
-  // Implementations must invoke either RenewConnectivityWatchLocked() or
-  // StopConnectivityWatchLocked() before returning.
+  // After StartConnectivityWatchLocked() is called, this method will be
+  // invoked whenever the subchannel's connectivity state changes.
+  // To stop watching, use CancelConnectivityWatchLocked().
   virtual void ProcessConnectivityChangeLocked(
       grpc_connectivity_state connectivity_state) GRPC_ABSTRACT;
 
+ private:
+  // Watcher for subchannel connectivity state.
+  class Watcher : public Subchannel::ConnectivityStateWatcher {
+   public:
+    Watcher(
+        SubchannelData<SubchannelListType, SubchannelDataType>* subchannel_data,
+        RefCountedPtr<SubchannelListType> subchannel_list)
+        : subchannel_data_(subchannel_data),
+          subchannel_list_(std::move(subchannel_list)) {}
+
+    ~Watcher() { subchannel_list_.reset(DEBUG_LOCATION, "Watcher dtor"); }
+
+    void OnConnectivityStateChange(
+        grpc_connectivity_state new_state,
+        RefCountedPtr<ConnectedSubchannel> connected_subchannel) override;
+
+    grpc_pollset_set* interested_parties() override {
+      return subchannel_list_->policy()->interested_parties();
+    }
+
+   private:
+    // A fire-and-forget class that bounces into the combiner to process
+    // a connectivity state update.
+    class Updater {
+     public:
+      Updater(
+          SubchannelData<SubchannelListType, SubchannelDataType>*
+              subchannel_data,
+          RefCountedPtr<SubchannelList<SubchannelListType, SubchannelDataType>>
+              subchannel_list,
+          grpc_connectivity_state state,
+          RefCountedPtr<ConnectedSubchannel> connected_subchannel);
+
+      ~Updater() {
+        subchannel_list_.reset(DEBUG_LOCATION, "Watcher::Updater dtor");
+      }
+
+     private:
+      static void OnUpdateLocked(void* arg, grpc_error* error);
+
+      SubchannelData<SubchannelListType, SubchannelDataType>* subchannel_data_;
+      RefCountedPtr<SubchannelList<SubchannelListType, SubchannelDataType>>
+          subchannel_list_;
+      const grpc_connectivity_state state_;
+      RefCountedPtr<ConnectedSubchannel> connected_subchannel_;
+      grpc_closure closure_;
+    };
+
+    SubchannelData<SubchannelListType, SubchannelDataType>* subchannel_data_;
+    RefCountedPtr<SubchannelListType> subchannel_list_;
+  };
+
   // Unrefs the subchannel.
   void UnrefSubchannelLocked(const char* reason);
 
- private:
-  // Updates connected_subchannel_ based on pending_connectivity_state_unsafe_.
-  // Returns true if the connectivity state should be reported.
-  bool UpdateConnectedSubchannelLocked();
-
-  static void OnConnectivityChangedLocked(void* arg, grpc_error* error);
-
   // Backpointer to owning subchannel list.  Not owned.
   SubchannelList<SubchannelListType, SubchannelDataType>* subchannel_list_;
-
-  // The subchannel and connected subchannel.
+  // The subchannel.
   Subchannel* subchannel_;
+  // Will be non-null when the subchannel's state is being watched.
+  Subchannel::ConnectivityStateWatcher* pending_watcher_ = nullptr;
+  // Data updated by the watcher.
+  grpc_connectivity_state connectivity_state_;
   RefCountedPtr<ConnectedSubchannel> connected_subchannel_;
-
-  // Notification that connectivity has changed on subchannel.
-  grpc_closure connectivity_changed_closure_;
-  // Is a connectivity notification pending?
-  bool connectivity_notification_pending_ = false;
-  // Connectivity state to be updated by
-  // grpc_subchannel_notify_on_state_change(), not guarded by
-  // the combiner.
-  grpc_connectivity_state pending_connectivity_state_unsafe_;
 };
 
 // A list of subchannels.
@@ -213,7 +235,9 @@ class SubchannelList : public InternallyRefCounted<SubchannelListType> {
   // Accessors.
   LoadBalancingPolicy* policy() const { return policy_; }
   TraceFlag* tracer() const { return tracer_; }
-  bool inhibit_health_checking() const { return inhibit_health_checking_; }
+  const char* health_check_service_name() const {
+    return health_check_service_name_.get();
+  }
 
   // Resets connection backoff of all subchannels.
   // TODO(roth): We will probably need to rethink this as part of moving
@@ -251,7 +275,7 @@ class SubchannelList : public InternallyRefCounted<SubchannelListType> {
 
   TraceFlag* tracer_;
 
-  bool inhibit_health_checking_;
+  UniquePtr<char> health_check_service_name_;
 
   grpc_combiner* combiner_;
 
@@ -268,6 +292,67 @@ class SubchannelList : public InternallyRefCounted<SubchannelListType> {
 // implementation -- no user-servicable parts below
 //
 
+//
+// SubchannelData::Watcher
+//
+
+template <typename SubchannelListType, typename SubchannelDataType>
+void SubchannelData<SubchannelListType, SubchannelDataType>::Watcher::
+    OnConnectivityStateChange(
+        grpc_connectivity_state new_state,
+        RefCountedPtr<ConnectedSubchannel> connected_subchannel) {
+  // Will delete itself.
+  New<Updater>(subchannel_data_,
+               subchannel_list_->Ref(DEBUG_LOCATION, "Watcher::Updater"),
+               new_state, std::move(connected_subchannel));
+}
+
+template <typename SubchannelListType, typename SubchannelDataType>
+SubchannelData<SubchannelListType, SubchannelDataType>::Watcher::Updater::
+    Updater(
+        SubchannelData<SubchannelListType, SubchannelDataType>* subchannel_data,
+        RefCountedPtr<SubchannelList<SubchannelListType, SubchannelDataType>>
+            subchannel_list,
+        grpc_connectivity_state state,
+        RefCountedPtr<ConnectedSubchannel> connected_subchannel)
+    : subchannel_data_(subchannel_data),
+      subchannel_list_(std::move(subchannel_list)),
+      state_(state),
+      connected_subchannel_(std::move(connected_subchannel)) {
+  GRPC_CLOSURE_INIT(&closure_, &OnUpdateLocked, this,
+                    grpc_combiner_scheduler(subchannel_list_->combiner_));
+  GRPC_CLOSURE_SCHED(&closure_, GRPC_ERROR_NONE);
+}
+
+template <typename SubchannelListType, typename SubchannelDataType>
+void SubchannelData<SubchannelListType, SubchannelDataType>::Watcher::Updater::
+    OnUpdateLocked(void* arg, grpc_error* error) {
+  Updater* self = static_cast<Updater*>(arg);
+  SubchannelData* sd = self->subchannel_data_;
+  if (GRPC_TRACE_FLAG_ENABLED(*sd->subchannel_list_->tracer())) {
+    gpr_log(GPR_INFO,
+            "[%s %p] subchannel list %p index %" PRIuPTR " of %" PRIuPTR
+            " (subchannel %p): connectivity changed: state=%s, "
+            "connected_subchannel=%p, shutting_down=%d, pending_watcher=%p",
+            sd->subchannel_list_->tracer()->name(),
+            sd->subchannel_list_->policy(), sd->subchannel_list_, sd->Index(),
+            sd->subchannel_list_->num_subchannels(), sd->subchannel_,
+            grpc_connectivity_state_name(self->state_),
+            self->connected_subchannel_.get(),
+            sd->subchannel_list_->shutting_down(), sd->pending_watcher_);
+  }
+  if (!sd->subchannel_list_->shutting_down() &&
+      sd->pending_watcher_ != nullptr) {
+    sd->connectivity_state_ = self->state_;
+    // Get or release ref to connected subchannel.
+    sd->connected_subchannel_ = std::move(self->connected_subchannel_);
+    // Call the subclass's ProcessConnectivityChangeLocked() method.
+    sd->ProcessConnectivityChangeLocked(sd->connectivity_state_);
+  }
+  // Clean up.
+  Delete(self);
+}
+
 //
 // SubchannelData
 //
@@ -275,23 +360,16 @@ class SubchannelList : public InternallyRefCounted<SubchannelListType> {
 template <typename SubchannelListType, typename SubchannelDataType>
 SubchannelData<SubchannelListType, SubchannelDataType>::SubchannelData(
     SubchannelList<SubchannelListType, SubchannelDataType>* subchannel_list,
-    const ServerAddress& address, Subchannel* subchannel,
-    grpc_combiner* combiner)
+    const ServerAddress& address, Subchannel* subchannel)
     : subchannel_list_(subchannel_list),
       subchannel_(subchannel),
       // We assume that the current state is IDLE.  If not, we'll get a
       // callback telling us that.
-      pending_connectivity_state_unsafe_(GRPC_CHANNEL_IDLE) {
-  GRPC_CLOSURE_INIT(
-      &connectivity_changed_closure_,
-      (&SubchannelData<SubchannelListType,
-                       SubchannelDataType>::OnConnectivityChangedLocked),
-      this, grpc_combiner_scheduler(combiner));
-}
+      connectivity_state_(GRPC_CHANNEL_IDLE) {}
 
 template <typename SubchannelListType, typename SubchannelDataType>
 SubchannelData<SubchannelListType, SubchannelDataType>::~SubchannelData() {
-  UnrefSubchannelLocked("subchannel_data_destroy");
+  GPR_ASSERT(subchannel_ == nullptr);
 }
 
 template <typename SubchannelListType, typename SubchannelDataType>
@@ -326,56 +404,19 @@ void SubchannelData<SubchannelListType,
   if (GRPC_TRACE_FLAG_ENABLED(*subchannel_list_->tracer())) {
     gpr_log(GPR_INFO,
             "[%s %p] subchannel list %p index %" PRIuPTR " of %" PRIuPTR
-            " (subchannel %p): starting watch: requesting connectivity change "
-            "notification (from %s)",
+            " (subchannel %p): starting watch (from %s)",
             subchannel_list_->tracer()->name(), subchannel_list_->policy(),
             subchannel_list_, Index(), subchannel_list_->num_subchannels(),
-            subchannel_,
-            grpc_connectivity_state_name(pending_connectivity_state_unsafe_));
+            subchannel_, grpc_connectivity_state_name(connectivity_state_));
   }
-  GPR_ASSERT(!connectivity_notification_pending_);
-  connectivity_notification_pending_ = true;
-  subchannel_list()->Ref(DEBUG_LOCATION, "connectivity_watch").release();
-  subchannel_->NotifyOnStateChange(
-      subchannel_list_->policy()->interested_parties(),
-      &pending_connectivity_state_unsafe_, &connectivity_changed_closure_,
-      subchannel_list_->inhibit_health_checking());
-}
-
-template <typename SubchannelListType, typename SubchannelDataType>
-void SubchannelData<SubchannelListType,
-                    SubchannelDataType>::RenewConnectivityWatchLocked() {
-  if (GRPC_TRACE_FLAG_ENABLED(*subchannel_list_->tracer())) {
-    gpr_log(GPR_INFO,
-            "[%s %p] subchannel list %p index %" PRIuPTR " of %" PRIuPTR
-            " (subchannel %p): renewing watch: requesting connectivity change "
-            "notification (from %s)",
-            subchannel_list_->tracer()->name(), subchannel_list_->policy(),
-            subchannel_list_, Index(), subchannel_list_->num_subchannels(),
-            subchannel_,
-            grpc_connectivity_state_name(pending_connectivity_state_unsafe_));
-  }
-  GPR_ASSERT(connectivity_notification_pending_);
-  subchannel_->NotifyOnStateChange(
-      subchannel_list_->policy()->interested_parties(),
-      &pending_connectivity_state_unsafe_, &connectivity_changed_closure_,
-      subchannel_list_->inhibit_health_checking());
-}
-
-template <typename SubchannelListType, typename SubchannelDataType>
-void SubchannelData<SubchannelListType,
-                    SubchannelDataType>::StopConnectivityWatchLocked() {
-  if (GRPC_TRACE_FLAG_ENABLED(*subchannel_list_->tracer())) {
-    gpr_log(GPR_INFO,
-            "[%s %p] subchannel list %p index %" PRIuPTR " of %" PRIuPTR
-            " (subchannel %p): stopping connectivity watch",
-            subchannel_list_->tracer()->name(), subchannel_list_->policy(),
-            subchannel_list_, Index(), subchannel_list_->num_subchannels(),
-            subchannel_);
-  }
-  GPR_ASSERT(connectivity_notification_pending_);
-  connectivity_notification_pending_ = false;
-  subchannel_list()->Unref(DEBUG_LOCATION, "connectivity_watch");
+  GPR_ASSERT(pending_watcher_ == nullptr);
+  pending_watcher_ =
+      New<Watcher>(this, subchannel_list()->Ref(DEBUG_LOCATION, "Watcher"));
+  subchannel_->WatchConnectivityState(
+      connectivity_state_,
+      UniquePtr<char>(
+          gpr_strdup(subchannel_list_->health_check_service_name())),
+      UniquePtr<Subchannel::ConnectivityStateWatcher>(pending_watcher_));
 }
 
 template <typename SubchannelListType, typename SubchannelDataType>
@@ -389,91 +430,17 @@ void SubchannelData<SubchannelListType, SubchannelDataType>::
             subchannel_list_, Index(), subchannel_list_->num_subchannels(),
             subchannel_, reason);
   }
-  GPR_ASSERT(connectivity_notification_pending_);
-  subchannel_->NotifyOnStateChange(nullptr, nullptr,
-                                   &connectivity_changed_closure_,
-                                   subchannel_list_->inhibit_health_checking());
-}
-
-template <typename SubchannelListType, typename SubchannelDataType>
-bool SubchannelData<SubchannelListType,
-                    SubchannelDataType>::UpdateConnectedSubchannelLocked() {
-  // If the subchannel is READY, take a ref to the connected subchannel.
-  if (pending_connectivity_state_unsafe_ == GRPC_CHANNEL_READY) {
-    connected_subchannel_ = subchannel_->connected_subchannel();
-    // If the subchannel became disconnected between the time that READY
-    // was reported and the time we got here (e.g., between when a
-    // notification callback is scheduled and when it was actually run in
-    // the combiner), then the connected subchannel may have disappeared out
-    // from under us.  In that case, we don't actually want to consider the
-    // subchannel to be in state READY.  Instead, we use IDLE as the
-    // basis for any future connectivity watch; this is the one state that
-    // the subchannel will never transition back into, so this ensures
-    // that we will get a notification for the next state, even if that state
-    // is READY again (e.g., if the subchannel has transitioned back to
-    // READY before the next watch gets requested).
-    if (connected_subchannel_ == nullptr) {
-      if (GRPC_TRACE_FLAG_ENABLED(*subchannel_list_->tracer())) {
-        gpr_log(GPR_INFO,
-                "[%s %p] subchannel list %p index %" PRIuPTR " of %" PRIuPTR
-                " (subchannel %p): state is READY but connected subchannel is "
-                "null; moving to state IDLE",
-                subchannel_list_->tracer()->name(), subchannel_list_->policy(),
-                subchannel_list_, Index(), subchannel_list_->num_subchannels(),
-                subchannel_);
-      }
-      pending_connectivity_state_unsafe_ = GRPC_CHANNEL_IDLE;
-      return false;
-    }
-  } else {
-    // For any state other than READY, unref the connected subchannel.
-    connected_subchannel_.reset();
+  if (pending_watcher_ != nullptr) {
+    subchannel_->CancelConnectivityStateWatch(
+        subchannel_list_->health_check_service_name(), pending_watcher_);
+    pending_watcher_ = nullptr;
   }
-  return true;
-}
-
-template <typename SubchannelListType, typename SubchannelDataType>
-void SubchannelData<SubchannelListType, SubchannelDataType>::
-    OnConnectivityChangedLocked(void* arg, grpc_error* error) {
-  SubchannelData* sd = static_cast<SubchannelData*>(arg);
-  if (GRPC_TRACE_FLAG_ENABLED(*sd->subchannel_list_->tracer())) {
-    gpr_log(
-        GPR_INFO,
-        "[%s %p] subchannel list %p index %" PRIuPTR " of %" PRIuPTR
-        " (subchannel %p): connectivity changed: state=%s, error=%s, "
-        "shutting_down=%d",
-        sd->subchannel_list_->tracer()->name(), sd->subchannel_list_->policy(),
-        sd->subchannel_list_, sd->Index(),
-        sd->subchannel_list_->num_subchannels(), sd->subchannel_,
-        grpc_connectivity_state_name(sd->pending_connectivity_state_unsafe_),
-        grpc_error_string(error), sd->subchannel_list_->shutting_down());
-  }
-  // If shutting down, unref subchannel and stop watching.
-  if (sd->subchannel_list_->shutting_down() || error == GRPC_ERROR_CANCELLED) {
-    sd->UnrefSubchannelLocked("connectivity_shutdown");
-    sd->StopConnectivityWatchLocked();
-    return;
-  }
-  // Get or release ref to connected subchannel.
-  if (!sd->UpdateConnectedSubchannelLocked()) {
-    // We don't want to report this connectivity state, so renew the watch.
-    sd->RenewConnectivityWatchLocked();
-    return;
-  }
-  // Call the subclass's ProcessConnectivityChangeLocked() method.
-  sd->ProcessConnectivityChangeLocked(sd->pending_connectivity_state_unsafe_);
 }
 
 template <typename SubchannelListType, typename SubchannelDataType>
 void SubchannelData<SubchannelListType, SubchannelDataType>::ShutdownLocked() {
-  // If there's a pending notification for this subchannel, cancel it;
-  // the callback is responsible for unreffing the subchannel.
-  // Otherwise, unref the subchannel directly.
-  if (connectivity_notification_pending_) {
-    CancelConnectivityWatchLocked("shutdown");
-  } else if (subchannel_ != nullptr) {
-    UnrefSubchannelLocked("shutdown");
-  }
+  if (pending_watcher_ != nullptr) CancelConnectivityWatchLocked("shutdown");
+  UnrefSubchannelLocked("shutdown");
 }
 
 //
@@ -496,14 +463,25 @@ SubchannelList<SubchannelListType, SubchannelDataType>::SubchannelList(
             tracer_->name(), policy, this, addresses.size());
   }
   subchannels_.reserve(addresses.size());
+  // Find health check service name.
+  const bool inhibit_health_checking = grpc_channel_arg_get_bool(
+      grpc_channel_args_find(&args, GRPC_ARG_INHIBIT_HEALTH_CHECKING), false);
+  if (!inhibit_health_checking) {
+    const char* health_check_service_name = grpc_channel_arg_get_string(
+        grpc_channel_args_find(&args, "grpc.temp.health_check"));
+    if (health_check_service_name != nullptr) {
+      health_check_service_name_.reset(gpr_strdup(health_check_service_name));
+    }
+  }
   // We need to remove the LB addresses in order to be able to compare the
   // subchannel keys of subchannels from a different batch of addresses.
-  // We also remove the inhibit-health-checking arg, since we are
+  // We also remove the health-checking-related args, since we are
   // handling that here.
-  inhibit_health_checking_ = grpc_channel_arg_get_bool(
-      grpc_channel_args_find(&args, GRPC_ARG_INHIBIT_HEALTH_CHECKING), false);
-  static const char* keys_to_remove[] = {GRPC_ARG_SUBCHANNEL_ADDRESS,
-                                         GRPC_ARG_INHIBIT_HEALTH_CHECKING};
+  // We remove the service config, since it will be passed into the
+  // subchannel via call context.
+  static const char* keys_to_remove[] = {
+      GRPC_ARG_SUBCHANNEL_ADDRESS, "grpc.temp.health_check",
+      GRPC_ARG_INHIBIT_HEALTH_CHECKING, GRPC_ARG_SERVICE_CONFIG};
   // Create a subchannel for each address.
   for (size_t i = 0; i < addresses.size(); i++) {
     // TODO(roth): we should ideally hide this from the LB policy code. In
@@ -549,7 +527,7 @@ SubchannelList<SubchannelListType, SubchannelDataType>::SubchannelList(
               address_uri);
       gpr_free(address_uri);
     }
-    subchannels_.emplace_back(this, addresses[i], subchannel, combiner);
+    subchannels_.emplace_back(this, addresses[i], subchannel);
   }
 }
 
diff --git a/src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.cc b/src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.cc
index 00358736a94..27d543363a3 100644
--- a/src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.cc
+++ b/src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.cc
@@ -32,12 +32,12 @@
 #include "src/core/ext/filters/client_channel/http_connect_handshaker.h"
 #include "src/core/ext/filters/client_channel/lb_policy_registry.h"
 #include "src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.h"
-#include "src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.h"
 #include "src/core/ext/filters/client_channel/resolver_registry.h"
 #include "src/core/ext/filters/client_channel/server_address.h"
 #include "src/core/ext/filters/client_channel/service_config.h"
 #include "src/core/lib/backoff/backoff.h"
 #include "src/core/lib/channel/channel_args.h"
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/host_port.h"
 #include "src/core/lib/gpr/string.h"
 #include "src/core/lib/gprpp/manual_constructor.h"
@@ -474,9 +474,8 @@ static bool should_use_ares(const char* resolver_env) {
 #endif /* GRPC_UV */
 
 void grpc_resolver_dns_ares_init() {
-  grpc_core::UniquePtr<char> resolver =
-      GPR_GLOBAL_CONFIG_GET(grpc_dns_resolver);
-  if (should_use_ares(resolver.get())) {
+  char* resolver_env = gpr_getenv("GRPC_DNS_RESOLVER");
+  if (should_use_ares(resolver_env)) {
     gpr_log(GPR_DEBUG, "Using ares dns resolver");
     address_sorting_init();
     grpc_error* error = grpc_ares_init();
@@ -492,15 +491,16 @@ void grpc_resolver_dns_ares_init() {
         grpc_core::UniquePtr<grpc_core::ResolverFactory>(
             grpc_core::New<grpc_core::AresDnsResolverFactory>()));
   }
+  gpr_free(resolver_env);
 }
 
 void grpc_resolver_dns_ares_shutdown() {
-  grpc_core::UniquePtr<char> resolver =
-      GPR_GLOBAL_CONFIG_GET(grpc_dns_resolver);
-  if (should_use_ares(resolver.get())) {
+  char* resolver_env = gpr_getenv("GRPC_DNS_RESOLVER");
+  if (should_use_ares(resolver_env)) {
     address_sorting_shutdown();
     grpc_ares_cleanup();
   }
+  gpr_free(resolver_env);
 }
 
 #else /* GRPC_ARES == 1 */
diff --git a/src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.cc b/src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.cc
deleted file mode 100644
index 07a617c14d5..00000000000
--- a/src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.cc
+++ /dev/null
@@ -1,28 +0,0 @@
-//
-// Copyright 2019 gRPC authors.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-//
-
-// This is similar to the sockaddr resolver, except that it supports a
-// bunch of query args that are useful for dependency injection in tests.
-
-#include <grpc/support/port_platform.h>
-
-#include "src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.h"
-
-GPR_GLOBAL_CONFIG_DEFINE_STRING(
-    grpc_dns_resolver, "",
-    "Declares which DNS resolver to use. The default is ares if gRPC is built "
-    "with c-ares support. Otherwise, the value of this environment variable is "
-    "ignored.")
diff --git a/src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.h b/src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.h
deleted file mode 100644
index d0a3486ea38..00000000000
--- a/src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.h
+++ /dev/null
@@ -1,29 +0,0 @@
-/*
- *
- * Copyright 2019 gRPC authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-#ifndef GRPC_CORE_EXT_FILTERS_CLIENT_CHANNEL_RESOLVER_DNS_DNS_RESOLVER_SELECTION_H
-#define GRPC_CORE_EXT_FILTERS_CLIENT_CHANNEL_RESOLVER_DNS_DNS_RESOLVER_SELECTION_H
-
-#include <grpc/support/port_platform.h>
-
-#include "src/core/lib/gprpp/global_config.h"
-
-GPR_GLOBAL_CONFIG_DECLARE_STRING(grpc_dns_resolver);
-
-#endif /* GRPC_CORE_EXT_FILTERS_CLIENT_CHANNEL_RESOLVER_DNS_DNS_RESOLVER_SELECTION_H \
-        */
diff --git a/src/core/ext/filters/client_channel/resolver/dns/native/dns_resolver.cc b/src/core/ext/filters/client_channel/resolver/dns/native/dns_resolver.cc
index 5ab75d02793..164d308c0dd 100644
--- a/src/core/ext/filters/client_channel/resolver/dns/native/dns_resolver.cc
+++ b/src/core/ext/filters/client_channel/resolver/dns/native/dns_resolver.cc
@@ -26,11 +26,11 @@
 #include <grpc/support/string_util.h>
 #include <grpc/support/time.h>
 
-#include "src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.h"
 #include "src/core/ext/filters/client_channel/resolver_registry.h"
 #include "src/core/ext/filters/client_channel/server_address.h"
 #include "src/core/lib/backoff/backoff.h"
 #include "src/core/lib/channel/channel_args.h"
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/host_port.h"
 #include "src/core/lib/gpr/string.h"
 #include "src/core/lib/gprpp/manual_constructor.h"
@@ -274,9 +274,8 @@ class NativeDnsResolverFactory : public ResolverFactory {
 }  // namespace grpc_core
 
 void grpc_resolver_dns_native_init() {
-  grpc_core::UniquePtr<char> resolver =
-      GPR_GLOBAL_CONFIG_GET(grpc_dns_resolver);
-  if (gpr_stricmp(resolver.get(), "native") == 0) {
+  char* resolver_env = gpr_getenv("GRPC_DNS_RESOLVER");
+  if (resolver_env != nullptr && gpr_stricmp(resolver_env, "native") == 0) {
     gpr_log(GPR_DEBUG, "Using native dns resolver");
     grpc_core::ResolverRegistry::Builder::RegisterResolverFactory(
         grpc_core::UniquePtr<grpc_core::ResolverFactory>(
@@ -292,6 +291,7 @@ void grpc_resolver_dns_native_init() {
               grpc_core::New<grpc_core::NativeDnsResolverFactory>()));
     }
   }
+  gpr_free(resolver_env);
 }
 
 void grpc_resolver_dns_native_shutdown() {}
diff --git a/src/core/ext/filters/client_channel/resolving_lb_policy.cc b/src/core/ext/filters/client_channel/resolving_lb_policy.cc
index b6bc3eabc49..4e383f65dd1 100644
--- a/src/core/ext/filters/client_channel/resolving_lb_policy.cc
+++ b/src/core/ext/filters/client_channel/resolving_lb_policy.cc
@@ -536,7 +536,7 @@ void ResolvingLoadBalancingPolicy::OnResolverResultChangedLocked(
   if (process_resolver_result_ != nullptr) {
     grpc_error* service_config_error = GRPC_ERROR_NONE;
     service_config_changed = process_resolver_result_(
-        process_resolver_result_user_data_, result, &lb_policy_name,
+        process_resolver_result_user_data_, &result, &lb_policy_name,
         &lb_policy_config, &service_config_error);
     if (service_config_error != GRPC_ERROR_NONE) {
       service_config_error_string =
diff --git a/src/core/ext/filters/client_channel/resolving_lb_policy.h b/src/core/ext/filters/client_channel/resolving_lb_policy.h
index b7d99dcc7de..0ca6c9563f9 100644
--- a/src/core/ext/filters/client_channel/resolving_lb_policy.h
+++ b/src/core/ext/filters/client_channel/resolving_lb_policy.h
@@ -69,8 +69,7 @@ class ResolvingLoadBalancingPolicy : public LoadBalancingPolicy {
   // empty, it means that we don't have a valid service config to use, and we
   // should set the channel to be in TRANSIENT_FAILURE.
   typedef bool (*ProcessResolverResultCallback)(
-      void* user_data, const Resolver::Result& result,
-      const char** lb_policy_name,
+      void* user_data, Resolver::Result* result, const char** lb_policy_name,
       RefCountedPtr<ParsedLoadBalancingConfig>* lb_policy_config,
       grpc_error** service_config_error);
   // If error is set when this returns, then construction failed, and
diff --git a/src/core/ext/filters/client_channel/subchannel.cc b/src/core/ext/filters/client_channel/subchannel.cc
index a284e692b09..cd778976166 100644
--- a/src/core/ext/filters/client_channel/subchannel.cc
+++ b/src/core/ext/filters/client_channel/subchannel.cc
@@ -303,8 +303,7 @@ void SubchannelCall::IncrementRefCount(const grpc_core::DebugLocation& location,
 // Subchannel::ConnectedSubchannelStateWatcher
 //
 
-class Subchannel::ConnectedSubchannelStateWatcher
-    : public InternallyRefCounted<ConnectedSubchannelStateWatcher> {
+class Subchannel::ConnectedSubchannelStateWatcher {
  public:
   // Must be instantiated while holding c->mu.
   explicit ConnectedSubchannelStateWatcher(Subchannel* c) : subchannel_(c) {
@@ -312,38 +311,17 @@ class Subchannel::ConnectedSubchannelStateWatcher
     GRPC_SUBCHANNEL_WEAK_REF(subchannel_, "state_watcher");
     GRPC_SUBCHANNEL_WEAK_UNREF(subchannel_, "connecting");
     // Start watching for connectivity state changes.
-    // Callback uses initial ref to this.
     GRPC_CLOSURE_INIT(&on_connectivity_changed_, OnConnectivityChanged, this,
                       grpc_schedule_on_exec_ctx);
     c->connected_subchannel_->NotifyOnStateChange(c->pollset_set_,
                                                   &pending_connectivity_state_,
                                                   &on_connectivity_changed_);
-    // Start health check if needed.
-    grpc_connectivity_state health_state = GRPC_CHANNEL_READY;
-    if (c->health_check_service_name_ != nullptr) {
-      health_check_client_ = MakeOrphanable<HealthCheckClient>(
-          c->health_check_service_name_.get(), c->connected_subchannel_,
-          c->pollset_set_, c->channelz_node_);
-      GRPC_CLOSURE_INIT(&on_health_changed_, OnHealthChanged, this,
-                        grpc_schedule_on_exec_ctx);
-      Ref().release();  // Ref for health callback tracked manually.
-      health_check_client_->NotifyOnHealthChange(&health_state_,
-                                                 &on_health_changed_);
-      health_state = GRPC_CHANNEL_CONNECTING;
-    }
-    // Report initial state.
-    c->SetConnectivityStateLocked(GRPC_CHANNEL_READY, "subchannel_connected");
-    grpc_connectivity_state_set(&c->state_and_health_tracker_, health_state,
-                                "subchannel_connected");
   }
 
   ~ConnectedSubchannelStateWatcher() {
     GRPC_SUBCHANNEL_WEAK_UNREF(subchannel_, "state_watcher");
   }
 
-  // Must be called while holding subchannel_->mu.
-  void Orphan() override { health_check_client_.reset(); }
-
  private:
   static void OnConnectivityChanged(void* arg, grpc_error* error) {
     auto* self = static_cast<ConnectedSubchannelStateWatcher*>(arg);
@@ -363,20 +341,10 @@ class Subchannel::ConnectedSubchannelStateWatcher
                           self->pending_connectivity_state_));
             }
             c->connected_subchannel_.reset();
-            c->connected_subchannel_watcher_.reset();
-            self->last_connectivity_state_ = GRPC_CHANNEL_TRANSIENT_FAILURE;
-            c->SetConnectivityStateLocked(GRPC_CHANNEL_TRANSIENT_FAILURE,
-                                          "reflect_child");
-            grpc_connectivity_state_set(&c->state_and_health_tracker_,
-                                        GRPC_CHANNEL_TRANSIENT_FAILURE,
-                                        "reflect_child");
+            c->SetConnectivityStateLocked(GRPC_CHANNEL_TRANSIENT_FAILURE);
             c->backoff_begun_ = false;
             c->backoff_.Reset();
-            c->MaybeStartConnectingLocked();
-          } else {
-            self->last_connectivity_state_ = GRPC_CHANNEL_SHUTDOWN;
           }
-          self->health_check_client_.reset();
           break;
         }
         default: {
@@ -384,96 +352,246 @@ class Subchannel::ConnectedSubchannelStateWatcher
           // a callback for READY, because that was the state we started
           // this watch from.  And a connected subchannel should never go
           // from READY to CONNECTING or IDLE.
-          self->last_connectivity_state_ = self->pending_connectivity_state_;
-          c->SetConnectivityStateLocked(self->pending_connectivity_state_,
-                                        "reflect_child");
-          if (self->pending_connectivity_state_ != GRPC_CHANNEL_READY) {
-            grpc_connectivity_state_set(&c->state_and_health_tracker_,
-                                        self->pending_connectivity_state_,
-                                        "reflect_child");
-          }
+          c->SetConnectivityStateLocked(self->pending_connectivity_state_);
           c->connected_subchannel_->NotifyOnStateChange(
               nullptr, &self->pending_connectivity_state_,
               &self->on_connectivity_changed_);
-          self = nullptr;  // So we don't unref below.
+          return;  // So we don't delete ourself below.
         }
       }
     }
-    // Don't unref until we've released the lock, because this might
+    // Don't delete until we've released the lock, because this might
     // cause the subchannel (which contains the lock) to be destroyed.
-    if (self != nullptr) self->Unref();
-  }
-
-  static void OnHealthChanged(void* arg, grpc_error* error) {
-    auto* self = static_cast<ConnectedSubchannelStateWatcher*>(arg);
-    Subchannel* c = self->subchannel_;
-    {
-      MutexLock lock(&c->mu_);
-      if (self->health_state_ != GRPC_CHANNEL_SHUTDOWN &&
-          self->health_check_client_ != nullptr) {
-        if (self->last_connectivity_state_ == GRPC_CHANNEL_READY) {
-          grpc_connectivity_state_set(&c->state_and_health_tracker_,
-                                      self->health_state_, "health_changed");
-        }
-        self->health_check_client_->NotifyOnHealthChange(
-            &self->health_state_, &self->on_health_changed_);
-        self = nullptr;  // So we don't unref below.
-      }
-    }
-    // Don't unref until we've released the lock, because this might
-    // cause the subchannel (which contains the lock) to be destroyed.
-    if (self != nullptr) self->Unref();
+    Delete(self);
   }
 
   Subchannel* subchannel_;
   grpc_closure on_connectivity_changed_;
   grpc_connectivity_state pending_connectivity_state_ = GRPC_CHANNEL_READY;
-  grpc_connectivity_state last_connectivity_state_ = GRPC_CHANNEL_READY;
+};
+
+//
+// Subchannel::ConnectivityStateWatcherList
+//
+
+void Subchannel::ConnectivityStateWatcherList::AddWatcherLocked(
+    UniquePtr<ConnectivityStateWatcher> watcher) {
+  watcher->next_ = head_;
+  head_ = watcher.release();
+}
+
+void Subchannel::ConnectivityStateWatcherList::RemoveWatcherLocked(
+    ConnectivityStateWatcher* watcher) {
+  for (ConnectivityStateWatcher** w = &head_; *w != nullptr; w = &(*w)->next_) {
+    if (*w == watcher) {
+      *w = watcher->next_;
+      Delete(watcher);
+      return;
+    }
+  }
+  GPR_UNREACHABLE_CODE(return );
+}
+
+void Subchannel::ConnectivityStateWatcherList::NotifyLocked(
+    Subchannel* subchannel, grpc_connectivity_state state) {
+  for (ConnectivityStateWatcher* w = head_; w != nullptr; w = w->next_) {
+    RefCountedPtr<ConnectedSubchannel> connected_subchannel;
+    if (state == GRPC_CHANNEL_READY) {
+      connected_subchannel = subchannel->connected_subchannel_;
+    }
+    // TODO(roth): In principle, it seems wrong to send this notification
+    // to the watcher while holding the subchannel's mutex, since it could
+    // lead to a deadlock if the watcher calls back into the subchannel
+    // before returning back to us.  In practice, this doesn't happen,
+    // because the LB policy code that watches subchannels always bounces
+    // the notification into the client_channel control-plane combiner
+    // before processing it.  But if we ever have any other callers here,
+    // we will probably need to change this.
+    w->OnConnectivityStateChange(state, std::move(connected_subchannel));
+  }
+}
+
+void Subchannel::ConnectivityStateWatcherList::Clear() {
+  while (head_ != nullptr) {
+    ConnectivityStateWatcher* next = head_->next_;
+    Delete(head_);
+    head_ = next;
+  }
+}
+
+//
+// Subchannel::HealthWatcherMap::HealthWatcher
+//
+
+// State needed for tracking the connectivity state with a particular
+// health check service name.
+class Subchannel::HealthWatcherMap::HealthWatcher
+    : public InternallyRefCounted<HealthWatcher> {
+ public:
+  HealthWatcher(Subchannel* c, UniquePtr<char> health_check_service_name,
+                grpc_connectivity_state subchannel_state)
+      : subchannel_(c),
+        health_check_service_name_(std::move(health_check_service_name)),
+        state_(subchannel_state == GRPC_CHANNEL_READY ? GRPC_CHANNEL_CONNECTING
+                                                      : subchannel_state) {
+    GRPC_SUBCHANNEL_WEAK_REF(subchannel_, "health_watcher");
+    GRPC_CLOSURE_INIT(&on_health_changed_, OnHealthChanged, this,
+                      grpc_schedule_on_exec_ctx);
+    // If the subchannel is already connected, start health checking.
+    if (subchannel_state == GRPC_CHANNEL_READY) StartHealthCheckingLocked();
+  }
+
+  ~HealthWatcher() {
+    GRPC_SUBCHANNEL_WEAK_UNREF(subchannel_, "health_watcher");
+  }
+
+  const char* health_check_service_name() const {
+    return health_check_service_name_.get();
+  }
+
+  grpc_connectivity_state state() const { return state_; }
+
+  void AddWatcherLocked(grpc_connectivity_state initial_state,
+                        UniquePtr<ConnectivityStateWatcher> watcher) {
+    if (state_ != initial_state) {
+      RefCountedPtr<ConnectedSubchannel> connected_subchannel;
+      if (state_ == GRPC_CHANNEL_READY) {
+        connected_subchannel = subchannel_->connected_subchannel_;
+      }
+      watcher->OnConnectivityStateChange(state_,
+                                         std::move(connected_subchannel));
+    }
+    watcher_list_.AddWatcherLocked(std::move(watcher));
+  }
+
+  void RemoveWatcherLocked(ConnectivityStateWatcher* watcher) {
+    watcher_list_.RemoveWatcherLocked(watcher);
+  }
+
+  bool HasWatchers() const { return !watcher_list_.empty(); }
+
+  void NotifyLocked(grpc_connectivity_state state) {
+    if (state == GRPC_CHANNEL_READY) {
+      // If we had not already notified for CONNECTING state, do so now.
+      // (We may have missed this earlier, because if the transition
+      // from IDLE to CONNECTING to READY was too quick, the connected
+      // subchannel may not have sent us a notification for CONNECTING.)
+      if (state_ != GRPC_CHANNEL_CONNECTING) {
+        state_ = GRPC_CHANNEL_CONNECTING;
+        watcher_list_.NotifyLocked(subchannel_, state_);
+      }
+      // If we've become connected, start health checking.
+      StartHealthCheckingLocked();
+    } else {
+      state_ = state;
+      watcher_list_.NotifyLocked(subchannel_, state_);
+      // We're not connected, so stop health checking.
+      health_check_client_.reset();
+    }
+  }
+
+  void Orphan() override {
+    watcher_list_.Clear();
+    health_check_client_.reset();
+    Unref();
+  }
+
+ private:
+  void StartHealthCheckingLocked() {
+    GPR_ASSERT(health_check_client_ == nullptr);
+    health_check_client_ = MakeOrphanable<HealthCheckClient>(
+        health_check_service_name_.get(), subchannel_->connected_subchannel_,
+        subchannel_->pollset_set_, subchannel_->channelz_node_);
+    Ref().release();  // Ref for health callback tracked manually.
+    health_check_client_->NotifyOnHealthChange(&state_, &on_health_changed_);
+  }
+
+  static void OnHealthChanged(void* arg, grpc_error* error) {
+    auto* self = static_cast<HealthWatcher*>(arg);
+    Subchannel* c = self->subchannel_;
+    {
+      MutexLock lock(&c->mu_);
+      if (self->state_ != GRPC_CHANNEL_SHUTDOWN &&
+          self->health_check_client_ != nullptr) {
+        self->watcher_list_.NotifyLocked(c, self->state_);
+        // Renew watch.
+        self->health_check_client_->NotifyOnHealthChange(
+            &self->state_, &self->on_health_changed_);
+        return;  // So we don't unref below.
+      }
+    }
+    // Don't unref until we've released the lock, because this might
+    // cause the subchannel (which contains the lock) to be destroyed.
+    self->Unref();
+  }
+
+  Subchannel* subchannel_;
+  UniquePtr<char> health_check_service_name_;
   OrphanablePtr<HealthCheckClient> health_check_client_;
   grpc_closure on_health_changed_;
-  grpc_connectivity_state health_state_ = GRPC_CHANNEL_CONNECTING;
+  grpc_connectivity_state state_;
+  ConnectivityStateWatcherList watcher_list_;
 };
 
 //
-// Subchannel::ExternalStateWatcher
+// Subchannel::HealthWatcherMap
 //
 
-struct Subchannel::ExternalStateWatcher {
-  ExternalStateWatcher(Subchannel* subchannel, grpc_pollset_set* pollset_set,
-                       grpc_closure* notify)
-      : subchannel(subchannel), pollset_set(pollset_set), notify(notify) {
-    GRPC_SUBCHANNEL_WEAK_REF(subchannel, "external_state_watcher+init");
-    GRPC_CLOSURE_INIT(&on_state_changed, OnStateChanged, this,
-                      grpc_schedule_on_exec_ctx);
+void Subchannel::HealthWatcherMap::AddWatcherLocked(
+    Subchannel* subchannel, grpc_connectivity_state initial_state,
+    UniquePtr<char> health_check_service_name,
+    UniquePtr<ConnectivityStateWatcher> watcher) {
+  // If the health check service name is not already present in the map,
+  // add it.
+  auto it = map_.find(health_check_service_name.get());
+  HealthWatcher* health_watcher;
+  if (it == map_.end()) {
+    const char* key = health_check_service_name.get();
+    auto w = MakeOrphanable<HealthWatcher>(
+        subchannel, std::move(health_check_service_name), subchannel->state_);
+    health_watcher = w.get();
+    map_[key] = std::move(w);
+  } else {
+    health_watcher = it->second.get();
   }
+  // Add the watcher to the entry.
+  health_watcher->AddWatcherLocked(initial_state, std::move(watcher));
+}
 
-  static void OnStateChanged(void* arg, grpc_error* error) {
-    ExternalStateWatcher* w = static_cast<ExternalStateWatcher*>(arg);
-    grpc_closure* follow_up = w->notify;
-    if (w->pollset_set != nullptr) {
-      grpc_pollset_set_del_pollset_set(w->subchannel->pollset_set_,
-                                       w->pollset_set);
-    }
-    {
-      MutexLock lock(&w->subchannel->mu_);
-      if (w->subchannel->external_state_watcher_list_ == w) {
-        w->subchannel->external_state_watcher_list_ = w->next;
-      }
-      if (w->next != nullptr) w->next->prev = w->prev;
-      if (w->prev != nullptr) w->prev->next = w->next;
-    }
-    GRPC_SUBCHANNEL_WEAK_UNREF(w->subchannel, "external_state_watcher+done");
-    Delete(w);
-    GRPC_CLOSURE_SCHED(follow_up, GRPC_ERROR_REF(error));
+void Subchannel::HealthWatcherMap::RemoveWatcherLocked(
+    const char* health_check_service_name, ConnectivityStateWatcher* watcher) {
+  auto it = map_.find(health_check_service_name);
+  GPR_ASSERT(it != map_.end());
+  it->second->RemoveWatcherLocked(watcher);
+  // If we just removed the last watcher for this service name, remove
+  // the map entry.
+  if (!it->second->HasWatchers()) map_.erase(it);
+}
+
+void Subchannel::HealthWatcherMap::NotifyLocked(grpc_connectivity_state state) {
+  for (const auto& p : map_) {
+    p.second->NotifyLocked(state);
   }
+}
 
-  Subchannel* subchannel;
-  grpc_pollset_set* pollset_set;
-  grpc_closure* notify;
-  grpc_closure on_state_changed;
-  ExternalStateWatcher* next = nullptr;
-  ExternalStateWatcher* prev = nullptr;
-};
+grpc_connectivity_state
+Subchannel::HealthWatcherMap::CheckConnectivityStateLocked(
+    Subchannel* subchannel, const char* health_check_service_name) {
+  auto it = map_.find(health_check_service_name);
+  if (it == map_.end()) {
+    // If the health check service name is not found in the map, we're
+    // not currently doing a health check for that service name.  If the
+    // subchannel's state without health checking is READY, report
+    // CONNECTING, since that's what we'd be in as soon as we do start a
+    // watch.  Otherwise, report the channel's state without health checking.
+    return subchannel->state_ == GRPC_CHANNEL_READY ? GRPC_CHANNEL_CONNECTING
+                                                    : subchannel->state_;
+  }
+  HealthWatcher* health_watcher = it->second.get();
+  return health_watcher->state();
+}
+
+void Subchannel::HealthWatcherMap::ShutdownLocked() { map_.clear(); }
 
 //
 // Subchannel
@@ -560,13 +678,6 @@ Subchannel::Subchannel(SubchannelKey* key, grpc_connector* connector,
   if (new_args != nullptr) grpc_channel_args_destroy(new_args);
   GRPC_CLOSURE_INIT(&on_connecting_finished_, OnConnectingFinished, this,
                     grpc_schedule_on_exec_ctx);
-  grpc_connectivity_state_init(&state_tracker_, GRPC_CHANNEL_IDLE,
-                               "subchannel");
-  grpc_connectivity_state_init(&state_and_health_tracker_, GRPC_CHANNEL_IDLE,
-                               "subchannel");
-  health_check_service_name_ =
-      UniquePtr<char>(gpr_strdup(grpc_channel_arg_get_string(
-          grpc_channel_args_find(args_, "grpc.temp.health_check"))));
   const grpc_arg* arg = grpc_channel_args_find(args_, GRPC_ARG_ENABLE_CHANNELZ);
   const bool channelz_enabled =
       grpc_channel_arg_get_bool(arg, GRPC_ENABLE_CHANNELZ_DEFAULT);
@@ -593,8 +704,6 @@ Subchannel::~Subchannel() {
     channelz_node_->MarkSubchannelDestroyed();
   }
   grpc_channel_args_destroy(args_);
-  grpc_connectivity_state_destroy(&state_tracker_);
-  grpc_connectivity_state_destroy(&state_and_health_tracker_);
   grpc_connector_unref(connector_);
   grpc_pollset_set_destroy(pollset_set_);
   Delete(key_);
@@ -698,53 +807,65 @@ const char* Subchannel::GetTargetAddress() {
   return addr_str;
 }
 
-RefCountedPtr<ConnectedSubchannel> Subchannel::connected_subchannel() {
-  MutexLock lock(&mu_);
-  return connected_subchannel_;
-}
-
 channelz::SubchannelNode* Subchannel::channelz_node() {
   return channelz_node_.get();
 }
 
-grpc_connectivity_state Subchannel::CheckConnectivity(
-    bool inhibit_health_checking) {
-  grpc_connectivity_state_tracker* tracker =
-      inhibit_health_checking ? &state_tracker_ : &state_and_health_tracker_;
-  grpc_connectivity_state state = grpc_connectivity_state_check(tracker);
+grpc_connectivity_state Subchannel::CheckConnectivityState(
+    const char* health_check_service_name,
+    RefCountedPtr<ConnectedSubchannel>* connected_subchannel) {
+  MutexLock lock(&mu_);
+  grpc_connectivity_state state;
+  if (health_check_service_name == nullptr) {
+    state = state_;
+  } else {
+    state = health_watcher_map_.CheckConnectivityStateLocked(
+        this, health_check_service_name);
+  }
+  if (connected_subchannel != nullptr && state == GRPC_CHANNEL_READY) {
+    *connected_subchannel = connected_subchannel_;
+  }
   return state;
 }
 
-void Subchannel::NotifyOnStateChange(grpc_pollset_set* interested_parties,
-                                     grpc_connectivity_state* state,
-                                     grpc_closure* notify,
-                                     bool inhibit_health_checking) {
-  grpc_connectivity_state_tracker* tracker =
-      inhibit_health_checking ? &state_tracker_ : &state_and_health_tracker_;
-  ExternalStateWatcher* w;
-  if (state == nullptr) {
-    MutexLock lock(&mu_);
-    for (w = external_state_watcher_list_; w != nullptr; w = w->next) {
-      if (w->notify == notify) {
-        grpc_connectivity_state_notify_on_state_change(tracker, nullptr,
-                                                       &w->on_state_changed);
-      }
-    }
-  } else {
-    w = New<ExternalStateWatcher>(this, interested_parties, notify);
-    if (interested_parties != nullptr) {
-      grpc_pollset_set_add_pollset_set(pollset_set_, interested_parties);
-    }
-    MutexLock lock(&mu_);
-    if (external_state_watcher_list_ != nullptr) {
-      w->next = external_state_watcher_list_;
-      w->next->prev = w;
-    }
-    external_state_watcher_list_ = w;
-    grpc_connectivity_state_notify_on_state_change(tracker, state,
-                                                   &w->on_state_changed);
-    MaybeStartConnectingLocked();
+void Subchannel::WatchConnectivityState(
+    grpc_connectivity_state initial_state,
+    UniquePtr<char> health_check_service_name,
+    UniquePtr<ConnectivityStateWatcher> watcher) {
+  MutexLock lock(&mu_);
+  grpc_pollset_set* interested_parties = watcher->interested_parties();
+  if (interested_parties != nullptr) {
+    grpc_pollset_set_add_pollset_set(pollset_set_, interested_parties);
   }
+  if (health_check_service_name == nullptr) {
+    if (state_ != initial_state) {
+      watcher->OnConnectivityStateChange(state_, connected_subchannel_);
+    }
+    watcher_list_.AddWatcherLocked(std::move(watcher));
+  } else {
+    health_watcher_map_.AddWatcherLocked(this, initial_state,
+                                         std::move(health_check_service_name),
+                                         std::move(watcher));
+  }
+}
+
+void Subchannel::CancelConnectivityStateWatch(
+    const char* health_check_service_name, ConnectivityStateWatcher* watcher) {
+  MutexLock lock(&mu_);
+  grpc_pollset_set* interested_parties = watcher->interested_parties();
+  if (interested_parties != nullptr) {
+    grpc_pollset_set_del_pollset_set(pollset_set_, interested_parties);
+  }
+  if (health_check_service_name == nullptr) {
+    watcher_list_.RemoveWatcherLocked(watcher);
+  } else {
+    health_watcher_map_.RemoveWatcherLocked(health_check_service_name, watcher);
+  }
+}
+
+void Subchannel::AttemptToConnect() {
+  MutexLock lock(&mu_);
+  MaybeStartConnectingLocked();
 }
 
 void Subchannel::ResetBackoff() {
@@ -818,15 +939,19 @@ const char* SubchannelConnectivityStateChangeString(
 
 }  // namespace
 
-void Subchannel::SetConnectivityStateLocked(grpc_connectivity_state state,
-                                            const char* reason) {
+// Note: Must be called with a state that is different from the current state.
+void Subchannel::SetConnectivityStateLocked(grpc_connectivity_state state) {
+  state_ = state;
   if (channelz_node_ != nullptr) {
     channelz_node_->AddTraceEvent(
         channelz::ChannelTrace::Severity::Info,
         grpc_slice_from_static_string(
             SubchannelConnectivityStateChangeString(state)));
   }
-  grpc_connectivity_state_set(&state_tracker_, state, reason);
+  // Notify non-health watchers.
+  watcher_list_.NotifyLocked(this, state);
+  // Notify health watchers.
+  health_watcher_map_.NotifyLocked(state);
 }
 
 void Subchannel::MaybeStartConnectingLocked() {
@@ -842,11 +967,6 @@ void Subchannel::MaybeStartConnectingLocked() {
     // Already connected: don't restart.
     return;
   }
-  if (!grpc_connectivity_state_has_watchers(&state_tracker_) &&
-      !grpc_connectivity_state_has_watchers(&state_and_health_tracker_)) {
-    // Nobody is interested in connecting: so don't just yet.
-    return;
-  }
   connecting_ = true;
   GRPC_SUBCHANNEL_WEAK_REF(this, "connecting");
   if (!backoff_begun_) {
@@ -903,9 +1023,7 @@ void Subchannel::ContinueConnectingLocked() {
   next_attempt_deadline_ = backoff_.NextAttemptTime();
   args.deadline = std::max(next_attempt_deadline_, min_deadline);
   args.channel_args = args_;
-  SetConnectivityStateLocked(GRPC_CHANNEL_CONNECTING, "connecting");
-  grpc_connectivity_state_set(&state_and_health_tracker_,
-                              GRPC_CHANNEL_CONNECTING, "connecting");
+  SetConnectivityStateLocked(GRPC_CHANNEL_CONNECTING);
   grpc_connector_connect(connector_, &args, &connecting_result_,
                          &on_connecting_finished_);
 }
@@ -924,12 +1042,7 @@ void Subchannel::OnConnectingFinished(void* arg, grpc_error* error) {
       GRPC_SUBCHANNEL_WEAK_UNREF(c, "connecting");
     } else {
       gpr_log(GPR_INFO, "Connect failed: %s", grpc_error_string(error));
-      c->SetConnectivityStateLocked(GRPC_CHANNEL_TRANSIENT_FAILURE,
-                                    "connect_failed");
-      grpc_connectivity_state_set(&c->state_and_health_tracker_,
-                                  GRPC_CHANNEL_TRANSIENT_FAILURE,
-                                  "connect_failed");
-      c->MaybeStartConnectingLocked();
+      c->SetConnectivityStateLocked(GRPC_CHANNEL_TRANSIENT_FAILURE);
       GRPC_SUBCHANNEL_WEAK_UNREF(c, "connecting");
     }
   }
@@ -982,8 +1095,9 @@ bool Subchannel::PublishTransportLocked() {
   gpr_log(GPR_INFO, "New connected subchannel at %p for subchannel %p",
           connected_subchannel_.get(), this);
   // Instantiate state watcher.  Will clean itself up.
-  connected_subchannel_watcher_ =
-      MakeOrphanable<ConnectedSubchannelStateWatcher>(this);
+  New<ConnectedSubchannelStateWatcher>(this);
+  // Report initial state.
+  SetConnectivityStateLocked(GRPC_CHANNEL_READY);
   return true;
 }
 
@@ -1000,7 +1114,7 @@ void Subchannel::Disconnect() {
   grpc_connector_shutdown(connector_, GRPC_ERROR_CREATE_FROM_STATIC_STRING(
                                           "Subchannel disconnected"));
   connected_subchannel_.reset();
-  connected_subchannel_watcher_.reset();
+  health_watcher_map_.ShutdownLocked();
 }
 
 gpr_atm Subchannel::RefMutate(
diff --git a/src/core/ext/filters/client_channel/subchannel.h b/src/core/ext/filters/client_channel/subchannel.h
index e3efc8900ae..e0741bb28fa 100644
--- a/src/core/ext/filters/client_channel/subchannel.h
+++ b/src/core/ext/filters/client_channel/subchannel.h
@@ -27,6 +27,7 @@
 #include "src/core/lib/backoff/backoff.h"
 #include "src/core/lib/channel/channel_stack.h"
 #include "src/core/lib/gprpp/arena.h"
+#include "src/core/lib/gprpp/map.h"
 #include "src/core/lib/gprpp/ref_counted.h"
 #include "src/core/lib/gprpp/ref_counted_ptr.h"
 #include "src/core/lib/gprpp/sync.h"
@@ -77,7 +78,7 @@ class ConnectedSubchannel : public RefCounted<ConnectedSubchannel> {
     grpc_millis deadline;
     Arena* arena;
     grpc_call_context_element* context;
-    grpc_core::CallCombiner* call_combiner;
+    CallCombiner* call_combiner;
     size_t parent_data_size;
   };
 
@@ -175,7 +176,38 @@ class SubchannelCall {
 // A subchannel that knows how to connect to exactly one target address. It
 // provides a target for load balancing.
 class Subchannel {
+ private:
+  class ConnectivityStateWatcherList;  // Forward declaration.
+
  public:
+  class ConnectivityStateWatcher {
+   public:
+    virtual ~ConnectivityStateWatcher() = default;
+
+    // Will be invoked whenever the subchannel's connectivity state
+    // changes.  There will be only one invocation of this method on a
+    // given watcher instance at any given time.
+    //
+    // When the state changes to READY, connected_subchannel will
+    // contain a ref to the connected subchannel.  When it changes from
+    // READY to some other state, the implementation must release its
+    // ref to the connected subchannel.
+    virtual void OnConnectivityStateChange(
+        grpc_connectivity_state new_state,
+        RefCountedPtr<ConnectedSubchannel> connected_subchannel)  // NOLINT
+        GRPC_ABSTRACT;
+
+    virtual grpc_pollset_set* interested_parties() GRPC_ABSTRACT;
+
+    GRPC_ABSTRACT_BASE_CLASS
+
+   private:
+    // For access to next_.
+    friend class Subchannel::ConnectivityStateWatcherList;
+
+    ConnectivityStateWatcher* next_ = nullptr;
+  };
+
   // The ctor and dtor are not intended to use directly.
   Subchannel(SubchannelKey* key, grpc_connector* connector,
              const grpc_channel_args* args);
@@ -201,20 +233,36 @@ class Subchannel {
   // Caller doesn't take ownership.
   const char* GetTargetAddress();
 
-  // Gets the connected subchannel - or nullptr if not connected (which may
-  // happen before it initially connects or during transient failures).
-  RefCountedPtr<ConnectedSubchannel> connected_subchannel();
-
   channelz::SubchannelNode* channelz_node();
 
-  // Polls the current connectivity state of the subchannel.
-  grpc_connectivity_state CheckConnectivity(bool inhibit_health_checking);
+  // Returns the current connectivity state of the subchannel.
+  // If health_check_service_name is non-null, the returned connectivity
+  // state will be based on the state reported by the backend for that
+  // service name.
+  // If the return value is GRPC_CHANNEL_READY, also sets *connected_subchannel.
+  grpc_connectivity_state CheckConnectivityState(
+      const char* health_check_service_name,
+      RefCountedPtr<ConnectedSubchannel>* connected_subchannel);
 
-  // When the connectivity state of the subchannel changes from \a *state,
-  // invokes \a notify and updates \a *state with the new state.
-  void NotifyOnStateChange(grpc_pollset_set* interested_parties,
-                           grpc_connectivity_state* state, grpc_closure* notify,
-                           bool inhibit_health_checking);
+  // Starts watching the subchannel's connectivity state.
+  // The first callback to the watcher will be delivered when the
+  // subchannel's connectivity state becomes a value other than
+  // initial_state, which may happen immediately.
+  // Subsequent callbacks will be delivered as the subchannel's state
+  // changes.
+  // The watcher will be destroyed either when the subchannel is
+  // destroyed or when CancelConnectivityStateWatch() is called.
+  void WatchConnectivityState(grpc_connectivity_state initial_state,
+                              UniquePtr<char> health_check_service_name,
+                              UniquePtr<ConnectivityStateWatcher> watcher);
+
+  // Cancels a connectivity state watch.
+  // If the watcher has already been destroyed, this is a no-op.
+  void CancelConnectivityStateWatch(const char* health_check_service_name,
+                                    ConnectivityStateWatcher* watcher);
+
+  // Attempt to connect to the backend.  Has no effect if already connected.
+  void AttemptToConnect();
 
   // Resets the connection backoff of the subchannel.
   // TODO(roth): Move connection backoff out of subchannels and up into LB
@@ -236,12 +284,62 @@ class Subchannel {
                                                  grpc_resolved_address* addr);
 
  private:
-  struct ExternalStateWatcher;
+  // A linked list of ConnectivityStateWatchers that are monitoring the
+  // subchannel's state.
+  class ConnectivityStateWatcherList {
+   public:
+    ~ConnectivityStateWatcherList() { Clear(); }
+
+    void AddWatcherLocked(UniquePtr<ConnectivityStateWatcher> watcher);
+    void RemoveWatcherLocked(ConnectivityStateWatcher* watcher);
+
+    // Notifies all watchers in the list about a change to state.
+    void NotifyLocked(Subchannel* subchannel, grpc_connectivity_state state);
+
+    void Clear();
+
+    bool empty() const { return head_ == nullptr; }
+
+   private:
+    ConnectivityStateWatcher* head_ = nullptr;
+  };
+
+  // A map that tracks ConnectivityStateWatchers using a particular health
+  // check service name.
+  //
+  // There is one entry in the map for each health check service name.
+  // Entries exist only as long as there are watchers using the
+  // corresponding service name.
+  //
+  // A health check client is maintained only while the subchannel is in
+  // state READY.
+  class HealthWatcherMap {
+   public:
+    void AddWatcherLocked(Subchannel* subchannel,
+                          grpc_connectivity_state initial_state,
+                          UniquePtr<char> health_check_service_name,
+                          UniquePtr<ConnectivityStateWatcher> watcher);
+    void RemoveWatcherLocked(const char* health_check_service_name,
+                             ConnectivityStateWatcher* watcher);
+
+    // Notifies the watcher when the subchannel's state changes.
+    void NotifyLocked(grpc_connectivity_state state);
+
+    grpc_connectivity_state CheckConnectivityStateLocked(
+        Subchannel* subchannel, const char* health_check_service_name);
+
+    void ShutdownLocked();
+
+   private:
+    class HealthWatcher;
+
+    Map<const char*, OrphanablePtr<HealthWatcher>, StringLess> map_;
+  };
+
   class ConnectedSubchannelStateWatcher;
 
   // Sets the subchannel's connectivity state to \a state.
-  void SetConnectivityStateLocked(grpc_connectivity_state state,
-                                  const char* reason);
+  void SetConnectivityStateLocked(grpc_connectivity_state state);
 
   // Methods for connection.
   void MaybeStartConnectingLocked();
@@ -279,15 +377,15 @@ class Subchannel {
   grpc_closure on_connecting_finished_;
   // Active connection, or null.
   RefCountedPtr<ConnectedSubchannel> connected_subchannel_;
-  OrphanablePtr<ConnectedSubchannelStateWatcher> connected_subchannel_watcher_;
   bool connecting_ = false;
   bool disconnected_ = false;
 
   // Connectivity state tracking.
-  grpc_connectivity_state_tracker state_tracker_;
-  grpc_connectivity_state_tracker state_and_health_tracker_;
-  UniquePtr<char> health_check_service_name_;
-  ExternalStateWatcher* external_state_watcher_list_ = nullptr;
+  grpc_connectivity_state state_ = GRPC_CHANNEL_IDLE;
+  // The list of watchers without a health check service name.
+  ConnectivityStateWatcherList watcher_list_;
+  // The map of watchers with health check service names.
+  HealthWatcherMap health_watcher_map_;
 
   // Backoff state.
   BackOff backoff_;
diff --git a/src/core/ext/transport/chttp2/transport/chttp2_plugin.cc b/src/core/ext/transport/chttp2/transport/chttp2_plugin.cc
index ac13d73d3b5..4c929d00ec9 100644
--- a/src/core/ext/transport/chttp2/transport/chttp2_plugin.cc
+++ b/src/core/ext/transport/chttp2/transport/chttp2_plugin.cc
@@ -23,11 +23,8 @@
 #include "src/core/lib/gprpp/global_config.h"
 #include "src/core/lib/transport/metadata.h"
 
-GPR_GLOBAL_CONFIG_DEFINE_BOOL(
-    grpc_experimental_disable_flow_control, false,
-    "If set, flow control will be effectively disabled. Max out all values and "
-    "assume the remote peer does the same. Thus we can ignore any flow control "
-    "bookkeeping, error checking, and decision making");
+GPR_GLOBAL_CONFIG_DEFINE_BOOL(grpc_experimental_disable_flow_control, false,
+                              "Disable flow control");
 
 void grpc_chttp2_plugin_init(void) {
   g_flow_control_enabled =
diff --git a/src/core/ext/transport/chttp2/transport/chttp2_transport.cc b/src/core/ext/transport/chttp2/transport/chttp2_transport.cc
index ccc3077f42b..4a04b9f1939 100644
--- a/src/core/ext/transport/chttp2/transport/chttp2_transport.cc
+++ b/src/core/ext/transport/chttp2/transport/chttp2_transport.cc
@@ -1720,7 +1720,7 @@ static void perform_stream_op(grpc_transport* gt, grpc_stream* gs,
 }
 
 static void cancel_pings(grpc_chttp2_transport* t, grpc_error* error) {
-  /* callback remaining pings: they're not allowed to call into the transpot,
+  /* callback remaining pings: they're not allowed to call into the transport,
      and maybe they hold resources that need to be freed */
   grpc_chttp2_ping_queue* pq = &t->ping_queue;
   GPR_ASSERT(error != GRPC_ERROR_NONE);
diff --git a/src/core/ext/transport/chttp2/transport/frame_data.cc b/src/core/ext/transport/chttp2/transport/frame_data.cc
index 6080a4bd1c4..3734c0150b7 100644
--- a/src/core/ext/transport/chttp2/transport/frame_data.cc
+++ b/src/core/ext/transport/chttp2/transport/frame_data.cc
@@ -104,23 +104,22 @@ grpc_error* grpc_deframe_unprocessed_incoming_frames(
     uint8_t* end = nullptr;
     uint8_t* cur = nullptr;
 
-    grpc_slice slice = grpc_slice_buffer_take_first(slices);
-
-    beg = GRPC_SLICE_START_PTR(slice);
-    end = GRPC_SLICE_END_PTR(slice);
+    grpc_slice* slice = grpc_slice_buffer_peek_first(slices);
+    beg = GRPC_SLICE_START_PTR(*slice);
+    end = GRPC_SLICE_END_PTR(*slice);
     cur = beg;
     uint32_t message_flags;
     char* msg;
 
     if (cur == end) {
-      grpc_slice_unref_internal(slice);
+      grpc_slice_buffer_remove_first(slices);
       continue;
     }
 
     switch (p->state) {
       case GRPC_CHTTP2_DATA_ERROR:
         p->state = GRPC_CHTTP2_DATA_ERROR;
-        grpc_slice_unref_internal(slice);
+        grpc_slice_buffer_remove_first(slices);
         return GRPC_ERROR_REF(p->error);
       case GRPC_CHTTP2_DATA_FH_0:
         s->stats.incoming.framing_bytes++;
@@ -138,19 +137,19 @@ grpc_error* grpc_deframe_unprocessed_incoming_frames(
             p->error = grpc_error_set_int(p->error, GRPC_ERROR_INT_STREAM_ID,
                                           static_cast<intptr_t>(s->id));
             gpr_free(msg);
-            msg = grpc_dump_slice(slice, GPR_DUMP_HEX | GPR_DUMP_ASCII);
+            msg = grpc_dump_slice(*slice, GPR_DUMP_HEX | GPR_DUMP_ASCII);
             p->error = grpc_error_set_str(p->error, GRPC_ERROR_STR_RAW_BYTES,
                                           grpc_slice_from_copied_string(msg));
             gpr_free(msg);
             p->error =
                 grpc_error_set_int(p->error, GRPC_ERROR_INT_OFFSET, cur - beg);
             p->state = GRPC_CHTTP2_DATA_ERROR;
-            grpc_slice_unref_internal(slice);
+            grpc_slice_buffer_remove_first(slices);
             return GRPC_ERROR_REF(p->error);
         }
         if (++cur == end) {
           p->state = GRPC_CHTTP2_DATA_FH_1;
-          grpc_slice_unref_internal(slice);
+          grpc_slice_buffer_remove_first(slices);
           continue;
         }
       /* fallthrough */
@@ -159,7 +158,7 @@ grpc_error* grpc_deframe_unprocessed_incoming_frames(
         p->frame_size = (static_cast<uint32_t>(*cur)) << 24;
         if (++cur == end) {
           p->state = GRPC_CHTTP2_DATA_FH_2;
-          grpc_slice_unref_internal(slice);
+          grpc_slice_buffer_remove_first(slices);
           continue;
         }
       /* fallthrough */
@@ -168,7 +167,7 @@ grpc_error* grpc_deframe_unprocessed_incoming_frames(
         p->frame_size |= (static_cast<uint32_t>(*cur)) << 16;
         if (++cur == end) {
           p->state = GRPC_CHTTP2_DATA_FH_3;
-          grpc_slice_unref_internal(slice);
+          grpc_slice_buffer_remove_first(slices);
           continue;
         }
       /* fallthrough */
@@ -177,7 +176,7 @@ grpc_error* grpc_deframe_unprocessed_incoming_frames(
         p->frame_size |= (static_cast<uint32_t>(*cur)) << 8;
         if (++cur == end) {
           p->state = GRPC_CHTTP2_DATA_FH_4;
-          grpc_slice_unref_internal(slice);
+          grpc_slice_buffer_remove_first(slices);
           continue;
         }
       /* fallthrough */
@@ -204,19 +203,18 @@ grpc_error* grpc_deframe_unprocessed_incoming_frames(
           p->state = GRPC_CHTTP2_DATA_FH_0;
         }
         s->pending_byte_stream = true;
-
         if (cur != end) {
-          grpc_slice_buffer_undo_take_first(
-              slices, grpc_slice_sub(slice, static_cast<size_t>(cur - beg),
-                                     static_cast<size_t>(end - beg)));
+          grpc_slice_buffer_sub_first(slices, static_cast<size_t>(cur - beg),
+                                      static_cast<size_t>(end - beg));
+        } else {
+          grpc_slice_buffer_remove_first(slices);
         }
-        grpc_slice_unref_internal(slice);
         return GRPC_ERROR_NONE;
       case GRPC_CHTTP2_DATA_FRAME: {
         GPR_ASSERT(p->parsing_frame != nullptr);
         GPR_ASSERT(slice_out != nullptr);
         if (cur == end) {
-          grpc_slice_unref_internal(slice);
+          grpc_slice_buffer_remove_first(slices);
           continue;
         }
         uint32_t remaining = static_cast<uint32_t>(end - cur);
@@ -224,32 +222,32 @@ grpc_error* grpc_deframe_unprocessed_incoming_frames(
           s->stats.incoming.data_bytes += remaining;
           if (GRPC_ERROR_NONE !=
               (error = p->parsing_frame->Push(
-                   grpc_slice_sub(slice, static_cast<size_t>(cur - beg),
+                   grpc_slice_sub(*slice, static_cast<size_t>(cur - beg),
                                   static_cast<size_t>(end - beg)),
                    slice_out))) {
-            grpc_slice_unref_internal(slice);
+            grpc_slice_buffer_remove_first(slices);
             return error;
           }
           if (GRPC_ERROR_NONE !=
               (error = p->parsing_frame->Finished(GRPC_ERROR_NONE, true))) {
-            grpc_slice_unref_internal(slice);
+            grpc_slice_buffer_remove_first(slices);
             return error;
           }
           p->parsing_frame = nullptr;
           p->state = GRPC_CHTTP2_DATA_FH_0;
-          grpc_slice_unref_internal(slice);
+          grpc_slice_buffer_remove_first(slices);
           return GRPC_ERROR_NONE;
         } else if (remaining < p->frame_size) {
           s->stats.incoming.data_bytes += remaining;
           if (GRPC_ERROR_NONE !=
               (error = p->parsing_frame->Push(
-                   grpc_slice_sub(slice, static_cast<size_t>(cur - beg),
+                   grpc_slice_sub(*slice, static_cast<size_t>(cur - beg),
                                   static_cast<size_t>(end - beg)),
                    slice_out))) {
             return error;
           }
           p->frame_size -= remaining;
-          grpc_slice_unref_internal(slice);
+          grpc_slice_buffer_remove_first(slices);
           return GRPC_ERROR_NONE;
         } else {
           GPR_ASSERT(remaining > p->frame_size);
@@ -257,30 +255,27 @@ grpc_error* grpc_deframe_unprocessed_incoming_frames(
           if (GRPC_ERROR_NONE !=
               p->parsing_frame->Push(
                   grpc_slice_sub(
-                      slice, static_cast<size_t>(cur - beg),
+                      *slice, static_cast<size_t>(cur - beg),
                       static_cast<size_t>(cur + p->frame_size - beg)),
                   slice_out)) {
-            grpc_slice_unref_internal(slice);
+            grpc_slice_buffer_remove_first(slices);
             return error;
           }
           if (GRPC_ERROR_NONE !=
               (error = p->parsing_frame->Finished(GRPC_ERROR_NONE, true))) {
-            grpc_slice_unref_internal(slice);
+            grpc_slice_buffer_remove_first(slices);
             return error;
           }
           p->parsing_frame = nullptr;
           p->state = GRPC_CHTTP2_DATA_FH_0;
           cur += p->frame_size;
-          grpc_slice_buffer_undo_take_first(
-              slices, grpc_slice_sub(slice, static_cast<size_t>(cur - beg),
-                                     static_cast<size_t>(end - beg)));
-          grpc_slice_unref_internal(slice);
+          grpc_slice_buffer_sub_first(slices, static_cast<size_t>(cur - beg),
+                                      static_cast<size_t>(end - beg));
           return GRPC_ERROR_NONE;
         }
       }
     }
   }
-
   return GRPC_ERROR_NONE;
 }
 
diff --git a/src/core/ext/transport/chttp2/transport/internal.h b/src/core/ext/transport/chttp2/transport/internal.h
index bfe77455e05..0322dc72837 100644
--- a/src/core/ext/transport/chttp2/transport/internal.h
+++ b/src/core/ext/transport/chttp2/transport/internal.h
@@ -225,14 +225,14 @@ class Chttp2IncomingByteStream : public ByteStream {
   // TODO(roth): When I converted this class to C++, I wanted to make it
   // inherit from RefCounted or InternallyRefCounted instead of continuing
   // to use its own custom ref-counting code.  However, that would require
-  // using multiple inheritence, which sucks in general.  And to make matters
+  // using multiple inheritance, which sucks in general.  And to make matters
   // worse, it causes problems with our New<> and Delete<> wrappers.
   // Specifically, unless RefCounted is first in the list of parent classes,
   // it will see a different value of the address of the object than the one
   // we actually allocated, in which case gpr_free() will be called on a
   // different address than the one we got from gpr_malloc(), thus causing a
   // crash.  Given the fragility of depending on that, as well as a desire to
-  // avoid multiple inheritence in general, I've decided to leave this
+  // avoid multiple inheritance in general, I've decided to leave this
   // alone for now.  We can revisit this once we're able to link against
   // libc++, at which point we can eliminate New<> and Delete<> and
   // switch to std::shared_ptr<>.
diff --git a/src/core/ext/transport/chttp2/transport/parsing.cc b/src/core/ext/transport/chttp2/transport/parsing.cc
index 15648c06fcd..1aa6d971684 100644
--- a/src/core/ext/transport/chttp2/transport/parsing.cc
+++ b/src/core/ext/transport/chttp2/transport/parsing.cc
@@ -28,6 +28,7 @@
 
 #include "src/core/lib/profiling/timers.h"
 #include "src/core/lib/slice/slice_string_helpers.h"
+#include "src/core/lib/slice/slice_utils.h"
 #include "src/core/lib/transport/http2_errors.h"
 #include "src/core/lib/transport/static_metadata.h"
 #include "src/core/lib/transport/status_conversion.h"
@@ -410,53 +411,42 @@ static void on_initial_header(void* tp, grpc_mdelem md) {
     gpr_free(value);
   }
 
-  if (GRPC_MDELEM_STORAGE(md) == GRPC_MDELEM_STORAGE_STATIC) {
-    // We don't use grpc_mdelem_eq here to avoid executing additional
-    // instructions. The reasoning is if the payload is not equal, we already
-    // know that the metadata elements are not equal because the md is
-    // confirmed to be static. If we had used grpc_mdelem_eq here, then if the
-    // payloads are not equal, grpc_mdelem_eq executes more instructions to
-    // determine if they're equal or not.
-    if (md.payload == GRPC_MDELEM_GRPC_STATUS_1.payload ||
-        md.payload == GRPC_MDELEM_GRPC_STATUS_2.payload) {
-      s->seen_error = true;
-    }
-  } else {
-    if (grpc_slice_eq(GRPC_MDKEY(md), GRPC_MDSTR_GRPC_STATUS) &&
-        !grpc_mdelem_eq(md, GRPC_MDELEM_GRPC_STATUS_0)) {
-      /* TODO(ctiller): check for a status like " 0" */
-      s->seen_error = true;
-    }
-
-    if (grpc_slice_eq(GRPC_MDKEY(md), GRPC_MDSTR_GRPC_TIMEOUT)) {
-      grpc_millis* cached_timeout = static_cast<grpc_millis*>(
-          grpc_mdelem_get_user_data(md, free_timeout));
-      grpc_millis timeout;
-      if (cached_timeout != nullptr) {
-        timeout = *cached_timeout;
-      } else {
-        if (GPR_UNLIKELY(
-                !grpc_http2_decode_timeout(GRPC_MDVALUE(md), &timeout))) {
-          char* val = grpc_slice_to_c_string(GRPC_MDVALUE(md));
-          gpr_log(GPR_ERROR, "Ignoring bad timeout value '%s'", val);
-          gpr_free(val);
-          timeout = GRPC_MILLIS_INF_FUTURE;
-        }
-        if (GRPC_MDELEM_IS_INTERNED(md)) {
-          /* store the result */
-          cached_timeout =
-              static_cast<grpc_millis*>(gpr_malloc(sizeof(grpc_millis)));
-          *cached_timeout = timeout;
-          grpc_mdelem_set_user_data(md, free_timeout, cached_timeout);
-        }
+  // If md.payload == GRPC_MDELEM_GRPC_STATUS_1 or GRPC_MDELEM_GRPC_STATUS_2,
+  // then we have seen an error. In fact, if it is a GRPC_STATUS and it's
+  // not equal to GRPC_MDELEM_GRPC_STATUS_0, then we have seen an error.
+  if (grpc_slice_eq_static_interned(GRPC_MDKEY(md), GRPC_MDSTR_GRPC_STATUS) &&
+      !grpc_mdelem_static_value_eq(md, GRPC_MDELEM_GRPC_STATUS_0)) {
+    /* TODO(ctiller): check for a status like " 0" */
+    s->seen_error = true;
+  } else if (grpc_slice_eq_static_interned(GRPC_MDKEY(md),
+                                           GRPC_MDSTR_GRPC_TIMEOUT)) {
+    grpc_millis* cached_timeout =
+        static_cast<grpc_millis*>(grpc_mdelem_get_user_data(md, free_timeout));
+    grpc_millis timeout;
+    if (cached_timeout != nullptr) {
+      timeout = *cached_timeout;
+    } else {
+      if (GPR_UNLIKELY(
+              !grpc_http2_decode_timeout(GRPC_MDVALUE(md), &timeout))) {
+        char* val = grpc_slice_to_c_string(GRPC_MDVALUE(md));
+        gpr_log(GPR_ERROR, "Ignoring bad timeout value '%s'", val);
+        gpr_free(val);
+        timeout = GRPC_MILLIS_INF_FUTURE;
       }
-      if (timeout != GRPC_MILLIS_INF_FUTURE) {
-        grpc_chttp2_incoming_metadata_buffer_set_deadline(
-            &s->metadata_buffer[0], grpc_core::ExecCtx::Get()->Now() + timeout);
+      if (GRPC_MDELEM_IS_INTERNED(md)) {
+        /* store the result */
+        cached_timeout =
+            static_cast<grpc_millis*>(gpr_malloc(sizeof(grpc_millis)));
+        *cached_timeout = timeout;
+        grpc_mdelem_set_user_data(md, free_timeout, cached_timeout);
       }
-      GRPC_MDELEM_UNREF(md);
-      return;
     }
+    if (timeout != GRPC_MILLIS_INF_FUTURE) {
+      grpc_chttp2_incoming_metadata_buffer_set_deadline(
+          &s->metadata_buffer[0], grpc_core::ExecCtx::Get()->Now() + timeout);
+    }
+    GRPC_MDELEM_UNREF(md);
+    return;
   }
 
   const size_t new_size = s->metadata_buffer[0].size + GRPC_MDELEM_LENGTH(md);
@@ -506,19 +496,11 @@ static void on_trailing_header(void* tp, grpc_mdelem md) {
     gpr_free(value);
   }
 
-  if (GRPC_MDELEM_STORAGE(md) == GRPC_MDELEM_STORAGE_STATIC) {
-    // We don't use grpc_mdelem_eq here to avoid executing additional
-    // instructions. The reasoning is if the payload is not equal, we already
-    // know that the metadata elements are not equal because the md is
-    // confirmed to be static. If we had used grpc_mdelem_eq here, then if the
-    // payloads are not equal, grpc_mdelem_eq executes more instructions to
-    // determine if they're equal or not.
-    if (md.payload == GRPC_MDELEM_GRPC_STATUS_1.payload ||
-        md.payload == GRPC_MDELEM_GRPC_STATUS_2.payload) {
-      s->seen_error = true;
-    }
-  } else if (grpc_slice_eq(GRPC_MDKEY(md), GRPC_MDSTR_GRPC_STATUS) &&
-             !grpc_mdelem_eq(md, GRPC_MDELEM_GRPC_STATUS_0)) {
+  // If md.payload == GRPC_MDELEM_GRPC_STATUS_1 or GRPC_MDELEM_GRPC_STATUS_2,
+  // then we have seen an error. In fact, if it is a GRPC_STATUS and it's
+  // not equal to GRPC_MDELEM_GRPC_STATUS_0, then we have seen an error.
+  if (grpc_slice_eq_static_interned(GRPC_MDKEY(md), GRPC_MDSTR_GRPC_STATUS) &&
+      !grpc_mdelem_static_value_eq(md, GRPC_MDELEM_GRPC_STATUS_0)) {
     /* TODO(ctiller): check for a status like " 0" */
     s->seen_error = true;
   }
diff --git a/src/core/ext/transport/cronet/transport/cronet_transport.cc b/src/core/ext/transport/cronet/transport/cronet_transport.cc
index 320b5297251..413de807638 100644
--- a/src/core/ext/transport/cronet/transport/cronet_transport.cc
+++ b/src/core/ext/transport/cronet/transport/cronet_transport.cc
@@ -753,15 +753,16 @@ static void convert_metadata_to_cronet_headers(
     } else {
       value = grpc_slice_to_c_string(GRPC_MDVALUE(mdelem));
     }
-    if (grpc_slice_eq(GRPC_MDKEY(mdelem), GRPC_MDSTR_SCHEME) ||
-        grpc_slice_eq(GRPC_MDKEY(mdelem), GRPC_MDSTR_AUTHORITY)) {
+    if (grpc_slice_eq_static_interned(GRPC_MDKEY(mdelem), GRPC_MDSTR_SCHEME) ||
+        grpc_slice_eq_static_interned(GRPC_MDKEY(mdelem),
+                                      GRPC_MDSTR_AUTHORITY)) {
       /* Cronet populates these fields on its own */
       gpr_free(key);
       gpr_free(value);
       continue;
     }
-    if (grpc_slice_eq(GRPC_MDKEY(mdelem), GRPC_MDSTR_METHOD)) {
-      if (grpc_slice_eq(GRPC_MDVALUE(mdelem), GRPC_MDSTR_PUT)) {
+    if (grpc_slice_eq_static_interned(GRPC_MDKEY(mdelem), GRPC_MDSTR_METHOD)) {
+      if (grpc_slice_eq_static_interned(GRPC_MDVALUE(mdelem), GRPC_MDSTR_PUT)) {
         *method = "PUT";
       } else {
         /* POST method in default*/
@@ -771,7 +772,7 @@ static void convert_metadata_to_cronet_headers(
       gpr_free(value);
       continue;
     }
-    if (grpc_slice_eq(GRPC_MDKEY(mdelem), GRPC_MDSTR_PATH)) {
+    if (grpc_slice_eq_static_interned(GRPC_MDKEY(mdelem), GRPC_MDSTR_PATH)) {
       /* Create URL by appending :path value to the hostname */
       gpr_asprintf(pp_url, "https://%s%s", host, value);
       gpr_free(key);
@@ -803,7 +804,8 @@ static void parse_grpc_header(const uint8_t* data, int* length,
 
 static bool header_has_authority(grpc_linked_mdelem* head) {
   while (head != nullptr) {
-    if (grpc_slice_eq(GRPC_MDKEY(head->md), GRPC_MDSTR_AUTHORITY)) {
+    if (grpc_slice_eq_static_interned(GRPC_MDKEY(head->md),
+                                      GRPC_MDSTR_AUTHORITY)) {
       return true;
     }
     head = head->next;
diff --git a/src/core/lib/compression/compression.cc b/src/core/lib/compression/compression.cc
index 9139fa04ee5..a3a069d9266 100644
--- a/src/core/lib/compression/compression.cc
+++ b/src/core/lib/compression/compression.cc
@@ -26,6 +26,7 @@
 #include "src/core/lib/compression/algorithm_metadata.h"
 #include "src/core/lib/compression/compression_internal.h"
 #include "src/core/lib/gpr/useful.h"
+#include "src/core/lib/slice/slice_utils.h"
 #include "src/core/lib/surface/api_trace.h"
 #include "src/core/lib/transport/static_metadata.h"
 
@@ -42,16 +43,17 @@ int grpc_compression_algorithm_is_stream(grpc_compression_algorithm algorithm) {
 
 int grpc_compression_algorithm_parse(grpc_slice name,
                                      grpc_compression_algorithm* algorithm) {
-  if (grpc_slice_eq(name, GRPC_MDSTR_IDENTITY)) {
+  if (grpc_slice_eq_static_interned(name, GRPC_MDSTR_IDENTITY)) {
     *algorithm = GRPC_COMPRESS_NONE;
     return 1;
-  } else if (grpc_slice_eq(name, GRPC_MDSTR_DEFLATE)) {
+  } else if (grpc_slice_eq_static_interned(name, GRPC_MDSTR_DEFLATE)) {
     *algorithm = GRPC_COMPRESS_DEFLATE;
     return 1;
-  } else if (grpc_slice_eq(name, GRPC_MDSTR_GZIP)) {
+  } else if (grpc_slice_eq_static_interned(name, GRPC_MDSTR_GZIP)) {
     *algorithm = GRPC_COMPRESS_GZIP;
     return 1;
-  } else if (grpc_slice_eq(name, GRPC_MDSTR_STREAM_SLASH_GZIP)) {
+  } else if (grpc_slice_eq_static_interned(name,
+                                           GRPC_MDSTR_STREAM_SLASH_GZIP)) {
     *algorithm = GRPC_COMPRESS_STREAM_GZIP;
     return 1;
   } else {
@@ -148,10 +150,13 @@ grpc_slice grpc_compression_algorithm_slice(
 
 grpc_compression_algorithm grpc_compression_algorithm_from_slice(
     const grpc_slice& str) {
-  if (grpc_slice_eq(str, GRPC_MDSTR_IDENTITY)) return GRPC_COMPRESS_NONE;
-  if (grpc_slice_eq(str, GRPC_MDSTR_DEFLATE)) return GRPC_COMPRESS_DEFLATE;
-  if (grpc_slice_eq(str, GRPC_MDSTR_GZIP)) return GRPC_COMPRESS_GZIP;
-  if (grpc_slice_eq(str, GRPC_MDSTR_STREAM_SLASH_GZIP))
+  if (grpc_slice_eq_static_interned(str, GRPC_MDSTR_IDENTITY))
+    return GRPC_COMPRESS_NONE;
+  if (grpc_slice_eq_static_interned(str, GRPC_MDSTR_DEFLATE))
+    return GRPC_COMPRESS_DEFLATE;
+  if (grpc_slice_eq_static_interned(str, GRPC_MDSTR_GZIP))
+    return GRPC_COMPRESS_GZIP;
+  if (grpc_slice_eq_static_interned(str, GRPC_MDSTR_STREAM_SLASH_GZIP))
     return GRPC_COMPRESS_STREAM_GZIP;
   return GRPC_COMPRESS_ALGORITHMS_COUNT;
 }
diff --git a/src/core/lib/compression/compression_internal.cc b/src/core/lib/compression/compression_internal.cc
index 65a36de4290..e0d73ef6d83 100644
--- a/src/core/lib/compression/compression_internal.cc
+++ b/src/core/lib/compression/compression_internal.cc
@@ -26,6 +26,7 @@
 #include "src/core/lib/compression/algorithm_metadata.h"
 #include "src/core/lib/compression/compression_internal.h"
 #include "src/core/lib/gpr/useful.h"
+#include "src/core/lib/slice/slice_utils.h"
 #include "src/core/lib/surface/api_trace.h"
 #include "src/core/lib/transport/static_metadata.h"
 
@@ -33,18 +34,21 @@
 
 grpc_message_compression_algorithm
 grpc_message_compression_algorithm_from_slice(const grpc_slice& str) {
-  if (grpc_slice_eq(str, GRPC_MDSTR_IDENTITY))
+  if (grpc_slice_eq_static_interned(str, GRPC_MDSTR_IDENTITY))
     return GRPC_MESSAGE_COMPRESS_NONE;
-  if (grpc_slice_eq(str, GRPC_MDSTR_DEFLATE))
+  if (grpc_slice_eq_static_interned(str, GRPC_MDSTR_DEFLATE))
     return GRPC_MESSAGE_COMPRESS_DEFLATE;
-  if (grpc_slice_eq(str, GRPC_MDSTR_GZIP)) return GRPC_MESSAGE_COMPRESS_GZIP;
+  if (grpc_slice_eq_static_interned(str, GRPC_MDSTR_GZIP))
+    return GRPC_MESSAGE_COMPRESS_GZIP;
   return GRPC_MESSAGE_COMPRESS_ALGORITHMS_COUNT;
 }
 
 grpc_stream_compression_algorithm grpc_stream_compression_algorithm_from_slice(
     const grpc_slice& str) {
-  if (grpc_slice_eq(str, GRPC_MDSTR_IDENTITY)) return GRPC_STREAM_COMPRESS_NONE;
-  if (grpc_slice_eq(str, GRPC_MDSTR_GZIP)) return GRPC_STREAM_COMPRESS_GZIP;
+  if (grpc_slice_eq_static_interned(str, GRPC_MDSTR_IDENTITY))
+    return GRPC_STREAM_COMPRESS_NONE;
+  if (grpc_slice_eq_static_interned(str, GRPC_MDSTR_GZIP))
+    return GRPC_STREAM_COMPRESS_GZIP;
   return GRPC_STREAM_COMPRESS_ALGORITHMS_COUNT;
 }
 
@@ -244,13 +248,13 @@ grpc_message_compression_algorithm grpc_message_compression_algorithm_for_level(
 
 int grpc_message_compression_algorithm_parse(
     grpc_slice value, grpc_message_compression_algorithm* algorithm) {
-  if (grpc_slice_eq(value, GRPC_MDSTR_IDENTITY)) {
+  if (grpc_slice_eq_static_interned(value, GRPC_MDSTR_IDENTITY)) {
     *algorithm = GRPC_MESSAGE_COMPRESS_NONE;
     return 1;
-  } else if (grpc_slice_eq(value, GRPC_MDSTR_DEFLATE)) {
+  } else if (grpc_slice_eq_static_interned(value, GRPC_MDSTR_DEFLATE)) {
     *algorithm = GRPC_MESSAGE_COMPRESS_DEFLATE;
     return 1;
-  } else if (grpc_slice_eq(value, GRPC_MDSTR_GZIP)) {
+  } else if (grpc_slice_eq_static_interned(value, GRPC_MDSTR_GZIP)) {
     *algorithm = GRPC_MESSAGE_COMPRESS_GZIP;
     return 1;
   } else {
@@ -263,10 +267,10 @@ int grpc_message_compression_algorithm_parse(
 
 int grpc_stream_compression_algorithm_parse(
     grpc_slice value, grpc_stream_compression_algorithm* algorithm) {
-  if (grpc_slice_eq(value, GRPC_MDSTR_IDENTITY)) {
+  if (grpc_slice_eq_static_interned(value, GRPC_MDSTR_IDENTITY)) {
     *algorithm = GRPC_STREAM_COMPRESS_NONE;
     return 1;
-  } else if (grpc_slice_eq(value, GRPC_MDSTR_GZIP)) {
+  } else if (grpc_slice_eq_static_interned(value, GRPC_MDSTR_GZIP)) {
     *algorithm = GRPC_STREAM_COMPRESS_GZIP;
     return 1;
   } else {
diff --git a/src/core/lib/compression/compression_internal.h b/src/core/lib/compression/compression_internal.h
index da007368b01..73947a2c34d 100644
--- a/src/core/lib/compression/compression_internal.h
+++ b/src/core/lib/compression/compression_internal.h
@@ -35,7 +35,7 @@ typedef enum {
   GRPC_MESSAGE_COMPRESS_ALGORITHMS_COUNT
 } grpc_message_compression_algorithm;
 
-/** Stream compresssion algorithms supported by gRPC */
+/** Stream compression algorithms supported by gRPC */
 typedef enum {
   GRPC_STREAM_COMPRESS_NONE = 0,
   GRPC_STREAM_COMPRESS_GZIP,
diff --git a/src/core/lib/compression/stream_compression.cc b/src/core/lib/compression/stream_compression.cc
index 46cb3daf4cc..e0857988643 100644
--- a/src/core/lib/compression/stream_compression.cc
+++ b/src/core/lib/compression/stream_compression.cc
@@ -22,6 +22,7 @@
 
 #include "src/core/lib/compression/stream_compression.h"
 #include "src/core/lib/compression/stream_compression_gzip.h"
+#include "src/core/lib/slice/slice_utils.h"
 
 extern const grpc_stream_compression_vtable
     grpc_stream_compression_identity_vtable;
@@ -65,11 +66,11 @@ void grpc_stream_compression_context_destroy(
 int grpc_stream_compression_method_parse(
     grpc_slice value, bool is_compress,
     grpc_stream_compression_method* method) {
-  if (grpc_slice_eq(value, GRPC_MDSTR_IDENTITY)) {
+  if (grpc_slice_eq_static_interned(value, GRPC_MDSTR_IDENTITY)) {
     *method = is_compress ? GRPC_STREAM_COMPRESSION_IDENTITY_COMPRESS
                           : GRPC_STREAM_COMPRESSION_IDENTITY_DECOMPRESS;
     return 1;
-  } else if (grpc_slice_eq(value, GRPC_MDSTR_GZIP)) {
+  } else if (grpc_slice_eq_static_interned(value, GRPC_MDSTR_GZIP)) {
     *method = is_compress ? GRPC_STREAM_COMPRESSION_GZIP_COMPRESS
                           : GRPC_STREAM_COMPRESSION_GZIP_DECOMPRESS;
     return 1;
diff --git a/src/core/lib/compression/stream_compression.h b/src/core/lib/compression/stream_compression.h
index c80f2f8692b..7328c3ec0f2 100644
--- a/src/core/lib/compression/stream_compression.h
+++ b/src/core/lib/compression/stream_compression.h
@@ -68,7 +68,7 @@ struct grpc_stream_compression_vtable {
  * at the end of compression. Emits at most \a max_output_size compressed bytes
  * into \a out. If all the bytes in input buffer \a in are depleted and \a flush
  * is not GRPC_STREAM_COMPRESSION_FLUSH_NONE, the corresponding flush method is
- * executed. The total number of bytes emitted is outputed in \a output_size.
+ * executed. The total number of bytes emitted is outputted in \a output_size.
  *
  * A SYNC flush indicates that the entire messages in \a in can be decompressed
  * from \a out. A FINISH flush implies a SYNC flush, and that any further
@@ -85,7 +85,7 @@ bool grpc_stream_compress(grpc_stream_compression_context* ctx,
  * Decompress bytes provided in \a in with a given context. Emits at most \a
  * max_output_size decompressed bytes into \a out. If decompression process
  * reached the end of a gzip stream, \a end_of_context is set to true; otherwise
- * it is set to false. The total number of bytes emitted is outputed in \a
+ * it is set to false. The total number of bytes emitted is outputted in \a
  * output_size.
  */
 bool grpc_stream_decompress(grpc_stream_compression_context* ctx,
diff --git a/src/core/lib/compression/stream_compression_gzip.cc b/src/core/lib/compression/stream_compression_gzip.cc
index bffdb1fd17d..452b22b7628 100644
--- a/src/core/lib/compression/stream_compression_gzip.cc
+++ b/src/core/lib/compression/stream_compression_gzip.cc
@@ -53,25 +53,25 @@ static bool gzip_flate(grpc_stream_compression_context_gzip* ctx,
     ctx->zs.avail_out = static_cast<uInt>(slice_size);
     ctx->zs.next_out = GRPC_SLICE_START_PTR(slice_out);
     while (ctx->zs.avail_out > 0 && in->length > 0 && !eoc) {
-      grpc_slice slice = grpc_slice_buffer_take_first(in);
-      ctx->zs.avail_in = static_cast<uInt> GRPC_SLICE_LENGTH(slice);
-      ctx->zs.next_in = GRPC_SLICE_START_PTR(slice);
+      grpc_slice* slice = grpc_slice_buffer_peek_first(in);
+      ctx->zs.avail_in = static_cast<uInt> GRPC_SLICE_LENGTH(*slice);
+      ctx->zs.next_in = GRPC_SLICE_START_PTR(*slice);
       r = ctx->flate(&ctx->zs, Z_NO_FLUSH);
       if (r < 0 && r != Z_BUF_ERROR) {
         gpr_log(GPR_ERROR, "zlib error (%d)", r);
         grpc_slice_unref_internal(slice_out);
-        grpc_slice_unref_internal(slice);
+        grpc_slice_buffer_remove_first(in);
         return false;
       } else if (r == Z_STREAM_END && ctx->flate == inflate) {
         eoc = true;
       }
       if (ctx->zs.avail_in > 0) {
-        grpc_slice_buffer_undo_take_first(
-            in,
-            grpc_slice_sub(slice, GRPC_SLICE_LENGTH(slice) - ctx->zs.avail_in,
-                           GRPC_SLICE_LENGTH(slice)));
+        grpc_slice_buffer_sub_first(
+            in, GRPC_SLICE_LENGTH(*slice) - ctx->zs.avail_in,
+            GRPC_SLICE_LENGTH(*slice));
+      } else {
+        grpc_slice_buffer_remove_first(in);
       }
-      grpc_slice_unref_internal(slice);
     }
     if (flush != 0 && ctx->zs.avail_out > 0 && !eoc) {
       GPR_ASSERT(in->length == 0);
diff --git a/src/core/lib/debug/trace.cc b/src/core/lib/debug/trace.cc
index 84c0a3805d3..cafdb15c699 100644
--- a/src/core/lib/debug/trace.cc
+++ b/src/core/lib/debug/trace.cc
@@ -26,11 +26,7 @@
 #include <grpc/grpc.h>
 #include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
-
-GPR_GLOBAL_CONFIG_DEFINE_STRING(
-    grpc_trace, "",
-    "A comma separated list of tracers that provide additional insight into "
-    "how gRPC C core is processing requests via debug logs.");
+#include "src/core/lib/gpr/env.h"
 
 int grpc_tracer_set_enabled(const char* name, int enabled);
 
@@ -137,14 +133,12 @@ static void parse(const char* s) {
   gpr_free(strings);
 }
 
-void grpc_tracer_init(const char* env_var_name) {
-  (void)env_var_name;  // suppress unused variable error
-  grpc_tracer_init();
-}
-
-void grpc_tracer_init() {
-  grpc_core::UniquePtr<char> value = GPR_GLOBAL_CONFIG_GET(grpc_trace);
-  parse(value.get());
+void grpc_tracer_init(const char* env_var) {
+  char* e = gpr_getenv(env_var);
+  if (e != nullptr) {
+    parse(e);
+    gpr_free(e);
+  }
 }
 
 void grpc_tracer_shutdown(void) {}
diff --git a/src/core/lib/debug/trace.h b/src/core/lib/debug/trace.h
index 6a4a8031ec4..72e1a4eded7 100644
--- a/src/core/lib/debug/trace.h
+++ b/src/core/lib/debug/trace.h
@@ -24,15 +24,7 @@
 #include <grpc/support/atm.h>
 #include <stdbool.h>
 
-#include "src/core/lib/gprpp/global_config.h"
-
-GPR_GLOBAL_CONFIG_DECLARE_STRING(grpc_trace);
-
-// TODO(veblush): Remove this deprecated function once codes depending on this
-// function are updated in the internal repo.
 void grpc_tracer_init(const char* env_var_name);
-
-void grpc_tracer_init();
 void grpc_tracer_shutdown(void);
 
 #if defined(__has_feature)
diff --git a/src/core/lib/gpr/env.h b/src/core/lib/gpr/env.h
index 11db17c83da..fb9e0636d10 100644
--- a/src/core/lib/gpr/env.h
+++ b/src/core/lib/gpr/env.h
@@ -26,7 +26,7 @@
 /* Env utility functions */
 
 /* Gets the environment variable value with the specified name.
-   Returns a newly allocated string. It is the responsability of the caller to
+   Returns a newly allocated string. It is the responsibility of the caller to
    gpr_free the return value if not NULL (which means that the environment
    variable exists). */
 char* gpr_getenv(const char* name);
@@ -34,6 +34,12 @@ char* gpr_getenv(const char* name);
 /* Sets the environment with the specified name to the specified value. */
 void gpr_setenv(const char* name, const char* value);
 
+/* This is a version of gpr_getenv that does not produce any output if it has to
+   use an insecure version of the function. It is ONLY to be used to solve the
+   problem in which we need to check an env variable to configure the verbosity
+   level of logging. So DO NOT USE THIS. */
+const char* gpr_getenv_silent(const char* name, char** dst);
+
 /* Deletes the variable name from the environment. */
 void gpr_unsetenv(const char* name);
 
diff --git a/src/core/lib/gpr/env_linux.cc b/src/core/lib/gpr/env_linux.cc
index 3a3aa541672..e84a9f6064c 100644
--- a/src/core/lib/gpr/env_linux.cc
+++ b/src/core/lib/gpr/env_linux.cc
@@ -38,7 +38,7 @@
 #include "src/core/lib/gpr/string.h"
 #include "src/core/lib/gpr/useful.h"
 
-static const char* gpr_getenv_silent(const char* name, char** dst) {
+const char* gpr_getenv_silent(const char* name, char** dst) {
   const char* insecure_func_used = nullptr;
   char* result = nullptr;
 #if defined(GPR_BACKWARDS_COMPATIBILITY_MODE)
diff --git a/src/core/lib/gpr/env_windows.cc b/src/core/lib/gpr/env_windows.cc
index 76c45fb87a7..72850a9587d 100644
--- a/src/core/lib/gpr/env_windows.cc
+++ b/src/core/lib/gpr/env_windows.cc
@@ -30,6 +30,11 @@
 #include "src/core/lib/gpr/string.h"
 #include "src/core/lib/gpr/string_windows.h"
 
+const char* gpr_getenv_silent(const char* name, char** dst) {
+  *dst = gpr_getenv(name);
+  return NULL;
+}
+
 char* gpr_getenv(const char* name) {
   char* result = NULL;
   DWORD size;
diff --git a/src/core/lib/gpr/log.cc b/src/core/lib/gpr/log.cc
index 8a229b2adf1..01ef112fb31 100644
--- a/src/core/lib/gpr/log.cc
+++ b/src/core/lib/gpr/log.cc
@@ -22,15 +22,12 @@
 #include <grpc/support/atm.h>
 #include <grpc/support/log.h>
 
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/string.h"
-#include "src/core/lib/gprpp/global_config.h"
 
 #include <stdio.h>
 #include <string.h>
 
-GPR_GLOBAL_CONFIG_DEFINE_STRING(grpc_verbosity, "ERROR",
-                                "Default gRPC logging verbosity")
-
 void gpr_default_log(gpr_log_func_args* args);
 static gpr_atm g_log_func = (gpr_atm)gpr_default_log;
 static gpr_atm g_min_severity_to_print = GPR_LOG_VERBOSITY_UNSET;
@@ -75,22 +72,29 @@ void gpr_set_log_verbosity(gpr_log_severity min_severity_to_print) {
 }
 
 void gpr_log_verbosity_init() {
-  grpc_core::UniquePtr<char> verbosity = GPR_GLOBAL_CONFIG_GET(grpc_verbosity);
+  char* verbosity = nullptr;
+  const char* insecure_getenv = gpr_getenv_silent("GRPC_VERBOSITY", &verbosity);
 
   gpr_atm min_severity_to_print = GPR_LOG_SEVERITY_ERROR;
-  if (strlen(verbosity.get()) > 0) {
-    if (gpr_stricmp(verbosity.get(), "DEBUG") == 0) {
+  if (verbosity != nullptr) {
+    if (gpr_stricmp(verbosity, "DEBUG") == 0) {
       min_severity_to_print = static_cast<gpr_atm>(GPR_LOG_SEVERITY_DEBUG);
-    } else if (gpr_stricmp(verbosity.get(), "INFO") == 0) {
+    } else if (gpr_stricmp(verbosity, "INFO") == 0) {
       min_severity_to_print = static_cast<gpr_atm>(GPR_LOG_SEVERITY_INFO);
-    } else if (gpr_stricmp(verbosity.get(), "ERROR") == 0) {
+    } else if (gpr_stricmp(verbosity, "ERROR") == 0) {
       min_severity_to_print = static_cast<gpr_atm>(GPR_LOG_SEVERITY_ERROR);
     }
+    gpr_free(verbosity);
   }
   if ((gpr_atm_no_barrier_load(&g_min_severity_to_print)) ==
       GPR_LOG_VERBOSITY_UNSET) {
     gpr_atm_no_barrier_store(&g_min_severity_to_print, min_severity_to_print);
   }
+
+  if (insecure_getenv != nullptr) {
+    gpr_log(GPR_DEBUG, "Warning: insecure environment read function '%s' used",
+            insecure_getenv);
+  }
 }
 
 void gpr_set_log_function(gpr_log_func f) {
diff --git a/src/core/lib/gprpp/fork.cc b/src/core/lib/gprpp/fork.cc
index cacf5e82e5a..fdc7c5354bd 100644
--- a/src/core/lib/gprpp/fork.cc
+++ b/src/core/lib/gprpp/fork.cc
@@ -26,8 +26,8 @@
 #include <grpc/support/sync.h>
 #include <grpc/support/time.h>
 
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/useful.h"
-#include "src/core/lib/gprpp/global_config.h"
 #include "src/core/lib/gprpp/memory.h"
 
 /*
@@ -35,16 +35,6 @@
  *       AROUND VERY SPECIFIC USE CASES.
  */
 
-#ifdef GRPC_ENABLE_FORK_SUPPORT
-#define GRPC_ENABLE_FORK_SUPPORT_DEFAULT true
-#else
-#define GRPC_ENABLE_FORK_SUPPORT_DEFAULT false
-#endif  // GRPC_ENABLE_FORK_SUPPORT
-
-GPR_GLOBAL_CONFIG_DEFINE_BOOL(grpc_enable_fork_support,
-                              GRPC_ENABLE_FORK_SUPPORT_DEFAULT,
-                              "Enable folk support");
-
 namespace grpc_core {
 namespace internal {
 // The exec_ctx_count has 2 modes, blocked and unblocked.
@@ -168,7 +158,34 @@ class ThreadState {
 
 void Fork::GlobalInit() {
   if (!override_enabled_) {
-    support_enabled_ = GPR_GLOBAL_CONFIG_GET(grpc_enable_fork_support);
+#ifdef GRPC_ENABLE_FORK_SUPPORT
+    support_enabled_ = true;
+#endif
+    bool env_var_set = false;
+    char* env = gpr_getenv("GRPC_ENABLE_FORK_SUPPORT");
+    if (env != nullptr) {
+      static const char* truthy[] = {"yes",  "Yes",  "YES", "true",
+                                     "True", "TRUE", "1"};
+      static const char* falsey[] = {"no",    "No",    "NO", "false",
+                                     "False", "FALSE", "0"};
+      for (size_t i = 0; i < GPR_ARRAY_SIZE(truthy); i++) {
+        if (0 == strcmp(env, truthy[i])) {
+          support_enabled_ = true;
+          env_var_set = true;
+          break;
+        }
+      }
+      if (!env_var_set) {
+        for (size_t i = 0; i < GPR_ARRAY_SIZE(falsey); i++) {
+          if (0 == strcmp(env, falsey[i])) {
+            support_enabled_ = false;
+            env_var_set = true;
+            break;
+          }
+        }
+      }
+      gpr_free(env);
+    }
   }
   if (support_enabled_) {
     exec_ctx_state_ = grpc_core::New<internal::ExecCtxState>();
@@ -243,7 +260,7 @@ void Fork::AwaitThreads() {
 
 internal::ExecCtxState* Fork::exec_ctx_state_ = nullptr;
 internal::ThreadState* Fork::thread_state_ = nullptr;
-bool Fork::support_enabled_ = false;
+std::atomic<bool> Fork::support_enabled_;
 bool Fork::override_enabled_ = false;
 Fork::child_postfork_func Fork::reset_child_polling_engine_ = nullptr;
 }  // namespace grpc_core
diff --git a/src/core/lib/gprpp/fork.h b/src/core/lib/gprpp/fork.h
index 5a7404f0d91..73f2fa56aa7 100644
--- a/src/core/lib/gprpp/fork.h
+++ b/src/core/lib/gprpp/fork.h
@@ -19,6 +19,10 @@
 #ifndef GRPC_CORE_LIB_GPRPP_FORK_H
 #define GRPC_CORE_LIB_GPRPP_FORK_H
 
+#include <grpc/support/port_platform.h>
+
+#include <atomic>
+
 /*
  * NOTE: FORKING IS NOT GENERALLY SUPPORTED, THIS IS ONLY INTENDED TO WORK
  *       AROUND VERY SPECIFIC USE CASES.
@@ -78,7 +82,7 @@ class Fork {
  private:
   static internal::ExecCtxState* exec_ctx_state_;
   static internal::ThreadState* thread_state_;
-  static bool support_enabled_;
+  static std::atomic<bool> support_enabled_;
   static bool override_enabled_;
   static child_postfork_func reset_child_polling_engine_;
 };
diff --git a/src/core/lib/gprpp/global_config_custom.h b/src/core/lib/gprpp/global_config_custom.h
index dd011fb34bf..175677e07c7 100644
--- a/src/core/lib/gprpp/global_config_custom.h
+++ b/src/core/lib/gprpp/global_config_custom.h
@@ -19,7 +19,7 @@
 #ifndef GRPC_CORE_LIB_GPRPP_GLOBAL_CONFIG_CUSTOM_H
 #define GRPC_CORE_LIB_GPRPP_GLOBAL_CONFIG_CUSTOM_H
 
-// This is a placeholder for custom global configuration implementaion.
+// This is a placeholder for custom global configuration implementation.
 // To use the custom one, please define following macros here.
 //
 //   GPR_GLOBAL_CONFIG_DEFINE_BOOL
diff --git a/src/core/lib/gprpp/ref_counted.h b/src/core/lib/gprpp/ref_counted.h
index 83e9429ba37..4de50985dcf 100644
--- a/src/core/lib/gprpp/ref_counted.h
+++ b/src/core/lib/gprpp/ref_counted.h
@@ -180,7 +180,7 @@ class RefCount {
 // So, use NonPolymorphicRefCount only when both of the following conditions
 // are guaranteed to hold:
 // (a) Child is a concrete leaf class in RefCounted<Child>, and
-// (b) you are gauranteed to call Unref only on concrete leaf classes and not
+// (b) you are guaranteed to call Unref only on concrete leaf classes and not
 //     their parents.
 //
 // The following example is illegal, because calling Unref() will not call
diff --git a/src/core/lib/iomgr/error_internal.h b/src/core/lib/iomgr/error_internal.h
index 80273960198..7b0cbd6d98f 100644
--- a/src/core/lib/iomgr/error_internal.h
+++ b/src/core/lib/iomgr/error_internal.h
@@ -49,7 +49,7 @@ struct grpc_error {
   uint8_t strs[GRPC_ERROR_STR_MAX];
   uint8_t times[GRPC_ERROR_TIME_MAX];
   // The child errors are stored in the arena, but are effectively a linked list
-  // structure, since they are contained withing grpc_linked_error objects.
+  // structure, since they are contained within grpc_linked_error objects.
   uint8_t first_err;
   uint8_t last_err;
   // The arena is dynamically reallocated with a grow factor of 1.5.
diff --git a/src/core/lib/iomgr/ev_epoll1_linux.cc b/src/core/lib/iomgr/ev_epoll1_linux.cc
index cacf7f94162..0c357dd2758 100644
--- a/src/core/lib/iomgr/ev_epoll1_linux.cc
+++ b/src/core/lib/iomgr/ev_epoll1_linux.cc
@@ -1031,7 +1031,7 @@ static grpc_error* pollset_work(grpc_pollset* ps,
        process the pending epoll events.
 
        The reason for decoupling do_epoll_wait and process_epoll_events is to
-       better distrubute the work (i.e handling epoll events) across multiple
+       better distribute the work (i.e handling epoll events) across multiple
        threads
 
        process_epoll_events() returns very quickly: It just queues the work on
diff --git a/src/core/lib/iomgr/ev_posix.cc b/src/core/lib/iomgr/ev_posix.cc
index ddafb7b5539..47cf5b83b17 100644
--- a/src/core/lib/iomgr/ev_posix.cc
+++ b/src/core/lib/iomgr/ev_posix.cc
@@ -31,19 +31,13 @@
 #include <grpc/support/string_util.h>
 
 #include "src/core/lib/debug/trace.h"
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/useful.h"
-#include "src/core/lib/gprpp/global_config.h"
 #include "src/core/lib/iomgr/ev_epoll1_linux.h"
 #include "src/core/lib/iomgr/ev_epollex_linux.h"
 #include "src/core/lib/iomgr/ev_poll_posix.h"
 #include "src/core/lib/iomgr/internal_errqueue.h"
 
-GPR_GLOBAL_CONFIG_DEFINE_STRING(
-    grpc_poll_strategy, "all",
-    "Declares which polling engines to try when starting gRPC. "
-    "This is a comma-separated list of engines, which are tried in priority "
-    "order first -> last.")
-
 grpc_core::TraceFlag grpc_polling_trace(false,
                                         "polling"); /* Disabled by default */
 
@@ -52,15 +46,16 @@ grpc_core::TraceFlag grpc_fd_trace(false, "fd_trace");
 grpc_core::DebugOnlyTraceFlag grpc_trace_fd_refcount(false, "fd_refcount");
 grpc_core::DebugOnlyTraceFlag grpc_polling_api_trace(false, "polling_api");
 
-// Polling API trace only enabled in debug builds
 #ifndef NDEBUG
+
+// Polling API trace only enabled in debug builds
 #define GRPC_POLLING_API_TRACE(format, ...)                  \
   if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_api_trace)) {     \
     gpr_log(GPR_INFO, "(polling-api) " format, __VA_ARGS__); \
   }
 #else
 #define GRPC_POLLING_API_TRACE(...)
-#endif  // NDEBUG
+#endif
 
 /** Default poll() function - a pointer so that it can be overridden by some
  *  tests */
@@ -71,7 +66,7 @@ int aix_poll(struct pollfd fds[], nfds_t nfds, int timeout) {
   return poll(fds, nfds, timeout);
 }
 grpc_poll_function_type grpc_poll_function = aix_poll;
-#endif  // GPR_AIX
+#endif
 
 grpc_wakeup_fd grpc_global_wakeup_fd;
 
@@ -210,11 +205,14 @@ void grpc_register_event_engine_factory(const char* name,
 const char* grpc_get_poll_strategy_name() { return g_poll_strategy_name; }
 
 void grpc_event_engine_init(void) {
-  grpc_core::UniquePtr<char> value = GPR_GLOBAL_CONFIG_GET(grpc_poll_strategy);
+  char* s = gpr_getenv("GRPC_POLL_STRATEGY");
+  if (s == nullptr) {
+    s = gpr_strdup("all");
+  }
 
   char** strings = nullptr;
   size_t nstrings = 0;
-  split(value.get(), &strings, &nstrings);
+  split(s, &strings, &nstrings);
 
   for (size_t i = 0; g_event_engine == nullptr && i < nstrings; i++) {
     try_engine(strings[i]);
@@ -226,10 +224,10 @@ void grpc_event_engine_init(void) {
   gpr_free(strings);
 
   if (g_event_engine == nullptr) {
-    gpr_log(GPR_ERROR, "No event engine could be initialized from %s",
-            value.get());
+    gpr_log(GPR_ERROR, "No event engine could be initialized from %s", s);
     abort();
   }
+  gpr_free(s);
 }
 
 void grpc_event_engine_shutdown(void) {
diff --git a/src/core/lib/iomgr/ev_posix.h b/src/core/lib/iomgr/ev_posix.h
index 30bb5e40faf..0ca3a6f82fd 100644
--- a/src/core/lib/iomgr/ev_posix.h
+++ b/src/core/lib/iomgr/ev_posix.h
@@ -24,14 +24,11 @@
 #include <poll.h>
 
 #include "src/core/lib/debug/trace.h"
-#include "src/core/lib/gprpp/global_config.h"
 #include "src/core/lib/iomgr/exec_ctx.h"
 #include "src/core/lib/iomgr/pollset.h"
 #include "src/core/lib/iomgr/pollset_set.h"
 #include "src/core/lib/iomgr/wakeup_fd_posix.h"
 
-GPR_GLOBAL_CONFIG_DECLARE_STRING(grpc_poll_strategy);
-
 extern grpc_core::TraceFlag grpc_fd_trace;      /* Disabled by default */
 extern grpc_core::TraceFlag grpc_polling_trace; /* Disabled by default */
 
diff --git a/src/core/lib/iomgr/fork_posix.cc b/src/core/lib/iomgr/fork_posix.cc
index 629b08162fb..7f8fb7e828b 100644
--- a/src/core/lib/iomgr/fork_posix.cc
+++ b/src/core/lib/iomgr/fork_posix.cc
@@ -28,6 +28,7 @@
 #include <grpc/grpc.h>
 #include <grpc/support/log.h>
 
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gprpp/fork.h"
 #include "src/core/lib/gprpp/thd.h"
 #include "src/core/lib/iomgr/ev_posix.h"
diff --git a/src/core/lib/iomgr/iomgr.cc b/src/core/lib/iomgr/iomgr.cc
index b86aa6f2d76..fd011788a06 100644
--- a/src/core/lib/iomgr/iomgr.cc
+++ b/src/core/lib/iomgr/iomgr.cc
@@ -42,8 +42,7 @@
 #include "src/core/lib/iomgr/timer_manager.h"
 
 GPR_GLOBAL_CONFIG_DEFINE_BOOL(grpc_abort_on_leaks, false,
-                              "A debugging aid to cause a call to abort() when "
-                              "gRPC objects are leaked past grpc_shutdown()");
+                              "Abort when leak is found");
 
 static gpr_mu g_mu;
 static gpr_cv g_rcv;
diff --git a/src/core/lib/iomgr/tcp_posix.cc b/src/core/lib/iomgr/tcp_posix.cc
index b9376b3ed0a..cda7bba0d3a 100644
--- a/src/core/lib/iomgr/tcp_posix.cc
+++ b/src/core/lib/iomgr/tcp_posix.cc
@@ -980,8 +980,7 @@ static bool tcp_flush(grpc_tcp* tcp, grpc_error** error) {
         // unref all and forget about all slices that have been written to this
         // point
         for (size_t idx = 0; idx < unwind_slice_idx; ++idx) {
-          grpc_slice_unref_internal(
-              grpc_slice_buffer_take_first(tcp->outgoing_buffer));
+          grpc_slice_buffer_remove_first(tcp->outgoing_buffer);
         }
         return false;
       } else if (errno == EPIPE) {
diff --git a/src/core/lib/iomgr/udp_server.cc b/src/core/lib/iomgr/udp_server.cc
index 5f8865ca57f..3e853945555 100644
--- a/src/core/lib/iomgr/udp_server.cc
+++ b/src/core/lib/iomgr/udp_server.cc
@@ -332,7 +332,7 @@ void GrpcUdpListener::OnFdAboutToOrphan() {
   GRPC_CLOSURE_INIT(&destroyed_closure_, destroyed_port, server_,
                     grpc_schedule_on_exec_ctx);
   if (!orphan_notified_ && udp_handler_ != nullptr) {
-    /* Singals udp_handler that the FD is about to be closed and
+    /* Signals udp_handler that the FD is about to be closed and
      * should no longer be used. */
     GRPC_CLOSURE_INIT(&orphan_fd_closure_, shutdown_fd, this,
                       grpc_schedule_on_exec_ctx);
@@ -645,7 +645,7 @@ int grpc_udp_server_add_port(grpc_udp_server* s,
           grpc_sockaddr_set_port(addr, allocated_port1);
           port = allocated_port1;
         } else if (allocated_port1 >= 0) {
-          /* The following sucessfully created socket should have same port as
+          /* The following successfully created socket should have same port as
            * the first one. */
           GPR_ASSERT(port == allocated_port1);
         }
diff --git a/src/core/lib/profiling/basic_timers.cc b/src/core/lib/profiling/basic_timers.cc
index 37689fe89d1..b19ad9fc23d 100644
--- a/src/core/lib/profiling/basic_timers.cc
+++ b/src/core/lib/profiling/basic_timers.cc
@@ -31,8 +31,7 @@
 #include <stdio.h>
 #include <string.h>
 
-#include "src/core/lib/gprpp/global_config.h"
-#include "src/core/lib/profiling/timers.h"
+#include "src/core/lib/gpr/env.h"
 
 typedef enum { BEGIN = '{', END = '}', MARK = '.' } marker_type;
 
@@ -75,16 +74,11 @@ static __thread int g_thread_id;
 static int g_next_thread_id;
 static int g_writing_enabled = 1;
 
-GPR_GLOBAL_CONFIG_DEFINE_STRING(grpc_latency_trace, "latency_trace.txt",
-                                "Output file name for latency trace")
-
 static const char* output_filename() {
   if (output_filename_or_null == NULL) {
-    grpc_core::UniquePtr<char> value =
-        GPR_GLOBAL_CONFIG_GET(grpc_latency_trace);
-    if (strlen(value.get()) > 0) {
-      output_filename_or_null = value.release();
-    } else {
+    output_filename_or_null = gpr_getenv("LATENCY_TRACE");
+    if (output_filename_or_null == NULL ||
+        strlen(output_filename_or_null) == 0) {
       output_filename_or_null = "latency_trace.txt";
     }
   }
diff --git a/src/core/lib/security/security_connector/load_system_roots_linux.cc b/src/core/lib/security/security_connector/load_system_roots_linux.cc
index 82d5bf6bcdd..924fa8a3e26 100644
--- a/src/core/lib/security/security_connector/load_system_roots_linux.cc
+++ b/src/core/lib/security/security_connector/load_system_roots_linux.cc
@@ -38,15 +38,12 @@
 #include <grpc/support/log.h>
 #include <grpc/support/string_util.h>
 
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/string.h"
 #include "src/core/lib/gpr/useful.h"
-#include "src/core/lib/gprpp/global_config.h"
 #include "src/core/lib/gprpp/inlined_vector.h"
 #include "src/core/lib/iomgr/load_file.h"
 
-GPR_GLOBAL_CONFIG_DEFINE_STRING(grpc_system_ssl_roots_dir, "",
-                                "Custom directory to SSL Roots");
-
 namespace grpc_core {
 namespace {
 
@@ -142,9 +139,10 @@ grpc_slice CreateRootCertsBundle(const char* certs_directory) {
 grpc_slice LoadSystemRootCerts() {
   grpc_slice result = grpc_empty_slice();
   // Prioritize user-specified custom directory if flag is set.
-  UniquePtr<char> custom_dir = GPR_GLOBAL_CONFIG_GET(grpc_system_ssl_roots_dir);
-  if (strlen(custom_dir.get()) > 0) {
-    result = CreateRootCertsBundle(custom_dir.get());
+  char* custom_dir = gpr_getenv("GRPC_SYSTEM_SSL_ROOTS_DIR");
+  if (custom_dir != nullptr) {
+    result = CreateRootCertsBundle(custom_dir);
+    gpr_free(custom_dir);
   }
   // If the custom directory is empty/invalid/not specified, fallback to
   // distribution-specific directory.
diff --git a/src/core/lib/security/security_connector/security_connector.cc b/src/core/lib/security/security_connector/security_connector.cc
index 47c0ad5aa3d..96a19605466 100644
--- a/src/core/lib/security/security_connector/security_connector.cc
+++ b/src/core/lib/security/security_connector/security_connector.cc
@@ -28,6 +28,7 @@
 #include "src/core/ext/transport/chttp2/alpn/alpn.h"
 #include "src/core/lib/channel/channel_args.h"
 #include "src/core/lib/channel/handshaker.h"
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/host_port.h"
 #include "src/core/lib/gpr/string.h"
 #include "src/core/lib/iomgr/load_file.h"
diff --git a/src/core/lib/security/security_connector/security_connector.h b/src/core/lib/security/security_connector/security_connector.h
index 4c74c5cfea0..f71ee54402d 100644
--- a/src/core/lib/security/security_connector/security_connector.h
+++ b/src/core/lib/security/security_connector/security_connector.h
@@ -102,7 +102,7 @@ class grpc_channel_security_connector : public grpc_security_connector {
                                grpc_auth_context* auth_context,
                                grpc_closure* on_call_host_checked,
                                grpc_error** error) GRPC_ABSTRACT;
-  /// Cancels a pending asychronous call to
+  /// Cancels a pending asynchronous call to
   /// grpc_channel_security_connector_check_call_host() with
   /// \a on_call_host_checked as its callback.
   virtual void cancel_check_call_host(grpc_closure* on_call_host_checked,
diff --git a/src/core/lib/security/security_connector/ssl/ssl_security_connector.cc b/src/core/lib/security/security_connector/ssl/ssl_security_connector.cc
index e76f4f15a7c..f920dc6046d 100644
--- a/src/core/lib/security/security_connector/ssl/ssl_security_connector.cc
+++ b/src/core/lib/security/security_connector/ssl/ssl_security_connector.cc
@@ -310,7 +310,7 @@ class grpc_ssl_server_security_connector
  private:
   /* Attempts to fetch the server certificate config if a callback is available.
    * Current certificate config will continue to be used if the callback returns
-   * an error. Returns true if new credentials were sucessfully loaded. */
+   * an error. Returns true if new credentials were successfully loaded. */
   bool try_fetch_ssl_server_credentials() {
     grpc_ssl_server_certificate_config* certificate_config = nullptr;
     bool status;
diff --git a/src/core/lib/security/security_connector/ssl_utils.cc b/src/core/lib/security/security_connector/ssl_utils.cc
index cb0d5437988..1eefff6fe24 100644
--- a/src/core/lib/security/security_connector/ssl_utils.cc
+++ b/src/core/lib/security/security_connector/ssl_utils.cc
@@ -27,6 +27,7 @@
 
 #include "src/core/ext/transport/chttp2/alpn/alpn.h"
 #include "src/core/lib/channel/channel_args.h"
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/host_port.h"
 #include "src/core/lib/gpr/string.h"
 #include "src/core/lib/gprpp/global_config.h"
@@ -45,13 +46,7 @@ static const char* installed_roots_path =
     INSTALL_PREFIX "/share/grpc/roots.pem";
 #endif
 
-/** Config variable that points to the default SSL roots file. This file
-   must be a PEM encoded file with all the roots such as the one that can be
-   downloaded from https://pki.google.com/roots.pem.  */
-GPR_GLOBAL_CONFIG_DEFINE_STRING(grpc_default_ssl_roots_file_path, "",
-                                "Path to the default SSL roots file.");
-
-/** Config variable used as a flag to enable/disable loading system root
+/** Environment variable used as a flag to enable/disable loading system root
     certificates from the OS trust store. */
 GPR_GLOBAL_CONFIG_DEFINE_BOOL(grpc_not_use_system_ssl_roots, false,
                               "Disable loading system root certificates.");
@@ -70,22 +65,20 @@ void grpc_set_ssl_roots_override_callback(grpc_ssl_roots_override_callback cb) {
 
 /* -- Cipher suites. -- */
 
+/* Defines the cipher suites that we accept by default. All these cipher suites
+   are compliant with HTTP2. */
+#define GRPC_SSL_CIPHER_SUITES     \
+  "ECDHE-ECDSA-AES128-GCM-SHA256:" \
+  "ECDHE-ECDSA-AES256-GCM-SHA384:" \
+  "ECDHE-RSA-AES128-GCM-SHA256:"   \
+  "ECDHE-RSA-AES256-GCM-SHA384"
+
 static gpr_once cipher_suites_once = GPR_ONCE_INIT;
 static const char* cipher_suites = nullptr;
 
-// All cipher suites for default are compliant with HTTP2.
-GPR_GLOBAL_CONFIG_DEFINE_STRING(
-    grpc_ssl_cipher_suites,
-    "ECDHE-ECDSA-AES128-GCM-SHA256:"
-    "ECDHE-ECDSA-AES256-GCM-SHA384:"
-    "ECDHE-RSA-AES128-GCM-SHA256:"
-    "ECDHE-RSA-AES256-GCM-SHA384",
-    "A colon separated list of cipher suites to use with OpenSSL")
-
 static void init_cipher_suites(void) {
-  grpc_core::UniquePtr<char> value =
-      GPR_GLOBAL_CONFIG_GET(grpc_ssl_cipher_suites);
-  cipher_suites = value.release();
+  char* overridden = gpr_getenv("GRPC_SSL_CIPHER_SUITES");
+  cipher_suites = overridden != nullptr ? overridden : GRPC_SSL_CIPHER_SUITES;
 }
 
 /* --- Util --- */
@@ -437,12 +430,13 @@ grpc_slice DefaultSslRootStore::ComputePemRootCerts() {
   grpc_slice result = grpc_empty_slice();
   const bool not_use_system_roots =
       GPR_GLOBAL_CONFIG_GET(grpc_not_use_system_ssl_roots);
-  // First try to load the roots from the configuration.
-  UniquePtr<char> default_root_certs_path =
-      GPR_GLOBAL_CONFIG_GET(grpc_default_ssl_roots_file_path);
-  if (strlen(default_root_certs_path.get()) > 0) {
-    GRPC_LOG_IF_ERROR(
-        "load_file", grpc_load_file(default_root_certs_path.get(), 1, &result));
+  // First try to load the roots from the environment.
+  char* default_root_certs_path =
+      gpr_getenv(GRPC_DEFAULT_SSL_ROOTS_FILE_PATH_ENV_VAR);
+  if (default_root_certs_path != nullptr) {
+    GRPC_LOG_IF_ERROR("load_file",
+                      grpc_load_file(default_root_certs_path, 1, &result));
+    gpr_free(default_root_certs_path);
   }
   // Try overridden roots if needed.
   grpc_ssl_roots_override_result ovrd_res = GRPC_SSL_ROOTS_OVERRIDE_FAIL;
diff --git a/src/core/lib/security/security_connector/ssl_utils.h b/src/core/lib/security/security_connector/ssl_utils.h
index 1765a344c2a..080e277f944 100644
--- a/src/core/lib/security/security_connector/ssl_utils.h
+++ b/src/core/lib/security/security_connector/ssl_utils.h
@@ -26,7 +26,6 @@
 #include <grpc/grpc_security.h>
 #include <grpc/slice_buffer.h>
 
-#include "src/core/lib/gprpp/global_config.h"
 #include "src/core/lib/gprpp/ref_counted_ptr.h"
 #include "src/core/lib/iomgr/error.h"
 #include "src/core/lib/security/security_connector/security_connector.h"
@@ -34,10 +33,7 @@
 #include "src/core/tsi/transport_security.h"
 #include "src/core/tsi/transport_security_interface.h"
 
-GPR_GLOBAL_CONFIG_DECLARE_STRING(grpc_default_ssl_roots_file_path);
-GPR_GLOBAL_CONFIG_DECLARE_BOOL(grpc_not_use_system_ssl_roots);
-
-/* --- Util --- */
+/* --- Util. --- */
 
 /* --- URL schemes. --- */
 #define GRPC_SSL_URL_SCHEME "https"
diff --git a/src/core/lib/security/transport/security_handshaker.cc b/src/core/lib/security/transport/security_handshaker.cc
index 3605bbe5974..fdc64727b96 100644
--- a/src/core/lib/security/transport/security_handshaker.cc
+++ b/src/core/lib/security/transport/security_handshaker.cc
@@ -144,11 +144,11 @@ size_t SecurityHandshaker::MoveReadBufferIntoHandshakeBuffer() {
   }
   size_t offset = 0;
   while (args_->read_buffer->count > 0) {
-    grpc_slice next_slice = grpc_slice_buffer_take_first(args_->read_buffer);
-    memcpy(handshake_buffer_ + offset, GRPC_SLICE_START_PTR(next_slice),
-           GRPC_SLICE_LENGTH(next_slice));
-    offset += GRPC_SLICE_LENGTH(next_slice);
-    grpc_slice_unref_internal(next_slice);
+    grpc_slice* next_slice = grpc_slice_buffer_peek_first(args_->read_buffer);
+    memcpy(handshake_buffer_ + offset, GRPC_SLICE_START_PTR(*next_slice),
+           GRPC_SLICE_LENGTH(*next_slice));
+    offset += GRPC_SLICE_LENGTH(*next_slice);
+    grpc_slice_buffer_remove_first(args_->read_buffer);
   }
   return bytes_in_read_buffer;
 }
diff --git a/src/core/lib/slice/b64.h b/src/core/lib/slice/b64.h
index 4475568c25b..88b880a4542 100644
--- a/src/core/lib/slice/b64.h
+++ b/src/core/lib/slice/b64.h
@@ -23,7 +23,7 @@
 
 #include <grpc/slice.h>
 
-/* Encodes data using base64. It is the caller's responsability to free
+/* Encodes data using base64. It is the caller's responsibility to free
    the returned char * using gpr_free. Returns NULL on NULL input.
    TODO(makdharma) : change the flags to bool from int */
 char* grpc_base64_encode(const void* data, size_t data_size, int url_safe,
@@ -35,7 +35,7 @@ size_t grpc_base64_estimate_encoded_size(size_t data_size, int url_safe,
                                          int multiline);
 
 /* Encodes data using base64 and write it to memory pointed to by result. It is
- * the caller's responsiblity to allocate enough memory in |result| to fit the
+ * the caller's responsibility to allocate enough memory in |result| to fit the
  * encoded data. */
 void grpc_base64_encode_core(char* result, const void* vdata, size_t data_size,
                              int url_safe, int multiline);
diff --git a/src/core/lib/slice/slice.cc b/src/core/lib/slice/slice.cc
index 2bf2b0f499f..75acb28e99c 100644
--- a/src/core/lib/slice/slice.cc
+++ b/src/core/lib/slice/slice.cc
@@ -410,6 +410,31 @@ int grpc_slice_eq(grpc_slice a, grpc_slice b) {
   return grpc_slice_default_eq_impl(a, b);
 }
 
+int grpc_slice_differs_refcounted(const grpc_slice& a,
+                                  const grpc_slice& b_not_inline) {
+  size_t a_len;
+  const uint8_t* a_ptr;
+  if (a.refcount) {
+    a_len = a.data.refcounted.length;
+    a_ptr = a.data.refcounted.bytes;
+  } else {
+    a_len = a.data.inlined.length;
+    a_ptr = &a.data.inlined.bytes[0];
+  }
+  if (a_len != b_not_inline.data.refcounted.length) {
+    return true;
+  }
+  if (a_len == 0) {
+    return false;
+  }
+  // This check *must* occur after the a_len == 0 check
+  // to retain compatibility with grpc_slice_eq.
+  if (a_ptr == nullptr) {
+    return true;
+  }
+  return memcmp(a_ptr, b_not_inline.data.refcounted.bytes, a_len);
+}
+
 int grpc_slice_cmp(grpc_slice a, grpc_slice b) {
   int d = static_cast<int>(GRPC_SLICE_LENGTH(a) - GRPC_SLICE_LENGTH(b));
   if (d != 0) return d;
diff --git a/src/core/lib/slice/slice_buffer.cc b/src/core/lib/slice/slice_buffer.cc
index 111d3c9578e..e1929250d4a 100644
--- a/src/core/lib/slice/slice_buffer.cc
+++ b/src/core/lib/slice/slice_buffer.cc
@@ -375,6 +375,24 @@ grpc_slice grpc_slice_buffer_take_first(grpc_slice_buffer* sb) {
   return slice;
 }
 
+void grpc_slice_buffer_remove_first(grpc_slice_buffer* sb) {
+  GPR_DEBUG_ASSERT(sb->count > 0);
+  sb->length -= GRPC_SLICE_LENGTH(sb->slices[0]);
+  grpc_slice_unref_internal(sb->slices[0]);
+  sb->slices++;
+  if (--sb->count == 0) {
+    sb->slices = sb->base_slices;
+  }
+}
+
+void grpc_slice_buffer_sub_first(grpc_slice_buffer* sb, size_t begin,
+                                 size_t end) {
+  // TODO(soheil): Introduce a ptr version for sub.
+  sb->length -= GRPC_SLICE_LENGTH(sb->slices[0]);
+  sb->slices[0] = grpc_slice_sub_no_ref(sb->slices[0], begin, end);
+  sb->length += end - begin;
+}
+
 void grpc_slice_buffer_undo_take_first(grpc_slice_buffer* sb,
                                        grpc_slice slice) {
   sb->slices--;
diff --git a/src/core/lib/slice/slice_intern.cc b/src/core/lib/slice/slice_intern.cc
index 0f190c186fa..15909d9b96f 100644
--- a/src/core/lib/slice/slice_intern.cc
+++ b/src/core/lib/slice/slice_intern.cc
@@ -19,6 +19,7 @@
 #include <grpc/support/port_platform.h>
 
 #include "src/core/lib/slice/slice_internal.h"
+#include "src/core/lib/slice/slice_utils.h"
 
 #include <inttypes.h>
 #include <string.h>
@@ -143,7 +144,8 @@ grpc_slice grpc_slice_maybe_static_intern(grpc_slice slice,
     static_metadata_hash_ent ent =
         static_metadata_hash[(hash + i) % GPR_ARRAY_SIZE(static_metadata_hash)];
     if (ent.hash == hash && ent.idx < GRPC_STATIC_MDSTR_COUNT &&
-        grpc_slice_eq(grpc_static_slice_table[ent.idx], slice)) {
+        grpc_slice_eq_static_interned(slice,
+                                      grpc_static_slice_table[ent.idx])) {
       *returned_slice_is_different = true;
       return grpc_static_slice_table[ent.idx];
     }
@@ -170,7 +172,8 @@ grpc_slice grpc_slice_intern(grpc_slice slice) {
     static_metadata_hash_ent ent =
         static_metadata_hash[(hash + i) % GPR_ARRAY_SIZE(static_metadata_hash)];
     if (ent.hash == hash && ent.idx < GRPC_STATIC_MDSTR_COUNT &&
-        grpc_slice_eq(grpc_static_slice_table[ent.idx], slice)) {
+        grpc_slice_eq_static_interned(slice,
+                                      grpc_static_slice_table[ent.idx])) {
       return grpc_static_slice_table[ent.idx];
     }
   }
@@ -183,7 +186,8 @@ grpc_slice grpc_slice_intern(grpc_slice slice) {
   /* search for an existing string */
   size_t idx = TABLE_IDX(hash, shard->capacity);
   for (s = shard->strs[idx]; s; s = s->bucket_next) {
-    if (s->hash == hash && grpc_slice_eq(slice, materialize(s))) {
+    if (s->hash == hash &&
+        grpc_slice_eq_static_interned(slice, materialize(s))) {
       if (s->refcnt.RefIfNonZero()) {
         gpr_mu_unlock(&shard->mu);
         return materialize(s);
diff --git a/src/core/lib/slice/slice_internal.h b/src/core/lib/slice/slice_internal.h
index a9f6087e11f..e4aba015315 100644
--- a/src/core/lib/slice/slice_internal.h
+++ b/src/core/lib/slice/slice_internal.h
@@ -21,6 +21,8 @@
 
 #include <grpc/support/port_platform.h>
 
+#include <grpc/support/log.h>
+
 #include <grpc/slice.h>
 #include <grpc/slice_buffer.h>
 #include <string.h>
@@ -240,6 +242,20 @@ void grpc_slice_buffer_partial_unref_internal(grpc_slice_buffer* sb,
                                               size_t idx);
 void grpc_slice_buffer_destroy_internal(grpc_slice_buffer* sb);
 
+// Returns a pointer to the first slice in the slice buffer without giving
+// ownership to or a reference count on that slice.
+inline grpc_slice* grpc_slice_buffer_peek_first(grpc_slice_buffer* sb) {
+  GPR_DEBUG_ASSERT(sb->count > 0);
+  return &sb->slices[0];
+}
+
+// Removes the first slice from the slice buffer.
+void grpc_slice_buffer_remove_first(grpc_slice_buffer* sb);
+
+// Calls grpc_slice_sub with the given parameters on the first slice.
+void grpc_slice_buffer_sub_first(grpc_slice_buffer* sb, size_t begin,
+                                 size_t end);
+
 /* Check if a slice is interned */
 bool grpc_slice_is_interned(const grpc_slice& slice);
 
diff --git a/src/core/lib/slice/slice_utils.h b/src/core/lib/slice/slice_utils.h
new file mode 100644
index 00000000000..7589bf8f0f7
--- /dev/null
+++ b/src/core/lib/slice/slice_utils.h
@@ -0,0 +1,50 @@
+/*
+ *
+ * Copyright 2019 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_SLICE_SLICE_UTILS_H
+#define GRPC_CORE_LIB_SLICE_SLICE_UTILS_H
+
+#include <grpc/support/port_platform.h>
+
+#include <grpc/slice.h>
+
+// When we compare two slices, and we know the latter is not inlined, we can
+// short circuit our comparison operator. We specifically use differs()
+// semantics instead of equals() semantics due to more favourable code
+// generation when using differs(). Specifically, we may use the output of
+// grpc_slice_differs_refcounted for control flow. If we use differs()
+// semantics, we end with a tailcall to memcmp(). If we use equals() semantics,
+// we need to invert the result that memcmp provides us, which costs several
+// instructions to do so. If we're using the result for control flow (i.e.
+// branching based on the output) then we're just performing the extra
+// operations to invert the result pointlessly. Concretely, we save 6 ops on
+// x86-64/clang with differs().
+int grpc_slice_differs_refcounted(const grpc_slice& a,
+                                  const grpc_slice& b_not_inline);
+// When we compare two slices, and we *know* that one of them is static or
+// interned, we can short circuit our slice equality function. The second slice
+// here must be static or interned; slice a can be any slice, inlined or not.
+inline bool grpc_slice_eq_static_interned(const grpc_slice& a,
+                                          const grpc_slice& b_static_interned) {
+  if (a.refcount == b_static_interned.refcount) {
+    return true;
+  }
+  return !grpc_slice_differs_refcounted(a, b_static_interned);
+}
+
+#endif /* GRPC_CORE_LIB_SLICE_SLICE_UTILS_H */
diff --git a/src/core/lib/surface/call.cc b/src/core/lib/surface/call.cc
index 275111f3213..254476f47e3 100644
--- a/src/core/lib/surface/call.cc
+++ b/src/core/lib/surface/call.cc
@@ -42,8 +42,8 @@
 #include "src/core/lib/gprpp/ref_counted.h"
 #include "src/core/lib/iomgr/timer.h"
 #include "src/core/lib/profiling/timers.h"
-#include "src/core/lib/slice/slice_internal.h"
 #include "src/core/lib/slice/slice_string_helpers.h"
+#include "src/core/lib/slice/slice_utils.h"
 #include "src/core/lib/surface/api_trace.h"
 #include "src/core/lib/surface/call.h"
 #include "src/core/lib/surface/call_test_only.h"
@@ -349,8 +349,8 @@ grpc_error* grpc_call_create(const grpc_call_create_args* args,
                MAX_SEND_EXTRA_METADATA_COUNT);
     for (size_t i = 0; i < args->add_initial_metadata_count; i++) {
       call->send_extra_metadata[i].md = args->add_initial_metadata[i];
-      if (grpc_slice_eq(GRPC_MDKEY(args->add_initial_metadata[i]),
-                        GRPC_MDSTR_PATH)) {
+      if (grpc_slice_eq_static_interned(
+              GRPC_MDKEY(args->add_initial_metadata[i]), GRPC_MDSTR_PATH)) {
         path = grpc_slice_ref_internal(
             GRPC_MDVALUE(args->add_initial_metadata[i]));
       }
diff --git a/src/core/lib/surface/init.cc b/src/core/lib/surface/init.cc
index 2a6d307ddab..1ed1a66b184 100644
--- a/src/core/lib/surface/init.cc
+++ b/src/core/lib/surface/init.cc
@@ -154,7 +154,7 @@ void grpc_init(void) {
      * at the appropriate time */
     grpc_register_security_filters();
     register_builtin_channel_init();
-    grpc_tracer_init();
+    grpc_tracer_init("GRPC_TRACE");
     /* no more changes to channel init pipelines */
     grpc_channel_init_finalize();
     grpc_iomgr_start();
diff --git a/src/core/lib/surface/version.cc b/src/core/lib/surface/version.cc
index 8aeadaf5078..7d9d49bc2aa 100644
--- a/src/core/lib/surface/version.cc
+++ b/src/core/lib/surface/version.cc
@@ -25,4 +25,4 @@
 
 const char* grpc_version_string(void) { return "7.0.0"; }
 
-const char* grpc_g_stands_for(void) { return "gandalf"; }
+const char* grpc_g_stands_for(void) { return "gale"; }
diff --git a/src/core/lib/transport/metadata.h b/src/core/lib/transport/metadata.h
index c0d1ab36351..3ff5a35dd2d 100644
--- a/src/core/lib/transport/metadata.h
+++ b/src/core/lib/transport/metadata.h
@@ -30,6 +30,7 @@
 #include "src/core/lib/gpr/useful.h"
 #include "src/core/lib/gprpp/atomic.h"
 #include "src/core/lib/gprpp/sync.h"
+#include "src/core/lib/slice/slice_utils.h"
 
 extern grpc_core::DebugOnlyTraceFlag grpc_trace_metadata;
 
@@ -138,7 +139,7 @@ bool grpc_mdelem_eq(grpc_mdelem a, grpc_mdelem b);
  * grpc_mdelem_eq and remove unnecessary checks. */
 inline bool grpc_mdelem_static_value_eq(grpc_mdelem a, grpc_mdelem b_static) {
   if (a.payload == b_static.payload) return true;
-  return grpc_slice_eq(GRPC_MDVALUE(a), GRPC_MDVALUE(b_static));
+  return grpc_slice_eq_static_interned(GRPC_MDVALUE(a), GRPC_MDVALUE(b_static));
 }
 
 /* Mutator and accessor for grpc_mdelem user data. The destructor function
diff --git a/src/core/lib/transport/static_metadata.cc b/src/core/lib/transport/static_metadata.cc
index fc5bb647573..61ee1d46f77 100644
--- a/src/core/lib/transport/static_metadata.cc
+++ b/src/core/lib/transport/static_metadata.cc
@@ -384,9 +384,9 @@ static const uint8_t elem_idxs[] = {
     52, 53, 54, 76,  69, 55,  56,  70, 58,  78,  80, 81, 82, 83, 59, 64,
     60, 75, 72, 255, 85, 255, 255, 68, 255, 255, 0};
 
-grpc_mdelem grpc_static_mdelem_for_static_strings(int a, int b) {
+grpc_mdelem grpc_static_mdelem_for_static_strings(intptr_t a, intptr_t b) {
   if (a == -1 || b == -1) return GRPC_MDNULL;
-  uint32_t k = (uint32_t)(a * 107 + b);
+  uint32_t k = static_cast<uint32_t>(a * 107 + b);
   uint32_t h = elems_phash(k);
   return h < GPR_ARRAY_SIZE(elem_keys) && elem_keys[h] == k &&
                  elem_idxs[h] != 255
diff --git a/src/core/lib/transport/static_metadata.h b/src/core/lib/transport/static_metadata.h
index 88293ae0613..a3f23de0953 100644
--- a/src/core/lib/transport/static_metadata.h
+++ b/src/core/lib/transport/static_metadata.h
@@ -29,6 +29,8 @@
 
 #include <grpc/support/port_platform.h>
 
+#include <cstdint>
+
 #include "src/core/lib/transport/metadata.h"
 
 #define GRPC_STATIC_MDSTR_COUNT 107
@@ -263,7 +265,8 @@ extern grpc_slice_refcount
    (slice).refcount->GetType() == grpc_slice_refcount::Type::STATIC)
 
 #define GRPC_STATIC_METADATA_INDEX(static_slice) \
-  ((int)((static_slice).refcount - grpc_static_metadata_refcounts))
+  (static_cast<intptr_t>(                        \
+      ((static_slice).refcount - grpc_static_metadata_refcounts)))
 
 #define GRPC_STATIC_MDELEM_COUNT 86
 extern grpc_mdelem_data grpc_static_mdelem_table[GRPC_STATIC_MDELEM_COUNT];
@@ -527,7 +530,7 @@ extern uintptr_t grpc_static_mdelem_user_data[GRPC_STATIC_MDELEM_COUNT];
 #define GRPC_MDELEM_ACCEPT_ENCODING_IDENTITY_COMMA_GZIP \
   (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[85], GRPC_MDELEM_STORAGE_STATIC))
 
-grpc_mdelem grpc_static_mdelem_for_static_strings(int a, int b);
+grpc_mdelem grpc_static_mdelem_for_static_strings(intptr_t a, intptr_t b);
 typedef enum {
   GRPC_BATCH_PATH,
   GRPC_BATCH_METHOD,
@@ -586,11 +589,11 @@ typedef union {
   } named;
 } grpc_metadata_batch_callouts;
 
-#define GRPC_BATCH_INDEX_OF(slice)                      \
-  (GRPC_IS_STATIC_METADATA_STRING((slice))              \
-       ? (grpc_metadata_batch_callouts_index)GPR_CLAMP( \
-             GRPC_STATIC_METADATA_INDEX((slice)), 0,    \
-             GRPC_BATCH_CALLOUTS_COUNT)                 \
+#define GRPC_BATCH_INDEX_OF(slice)                                        \
+  (GRPC_IS_STATIC_METADATA_STRING((slice))                                \
+       ? static_cast<grpc_metadata_batch_callouts_index>(                 \
+             GPR_CLAMP(GRPC_STATIC_METADATA_INDEX((slice)), 0,            \
+                       static_cast<intptr_t>(GRPC_BATCH_CALLOUTS_COUNT))) \
        : GRPC_BATCH_CALLOUTS_COUNT)
 
 extern const uint8_t grpc_static_accept_encoding_metadata[8];
diff --git a/src/core/tsi/alts/handshaker/alts_shared_resource.h b/src/core/tsi/alts/handshaker/alts_shared_resource.h
index 8ae0089a11c..d8638e7df69 100644
--- a/src/core/tsi/alts/handshaker/alts_shared_resource.h
+++ b/src/core/tsi/alts/handshaker/alts_shared_resource.h
@@ -48,7 +48,7 @@ alts_shared_resource_dedicated* grpc_alts_get_shared_resource_dedicated(void);
 
 /**
  * This method destroys the alts_shared_resource_dedicated object
- * shared by all TSI handshakes. The applicaiton is responsible for
+ * shared by all TSI handshakes. The application is responsible for
  * invoking the API before calling grpc_shutdown().
  */
 void grpc_alts_shared_resource_dedicated_shutdown();
diff --git a/src/cpp/common/version_cc.cc b/src/cpp/common/version_cc.cc
index 166c2d39b35..76e2773e938 100644
--- a/src/cpp/common/version_cc.cc
+++ b/src/cpp/common/version_cc.cc
@@ -22,5 +22,5 @@
 #include <grpcpp/grpcpp.h>
 
 namespace grpc {
-grpc::string Version() { return "1.21.0-dev"; }
+grpc::string Version() { return "1.22.0-dev"; }
 }  // namespace grpc
diff --git a/src/csharp/Grpc.Core.Api/VersionInfo.cs b/src/csharp/Grpc.Core.Api/VersionInfo.cs
index 1b2602e219d..fb67fe622b5 100644
--- a/src/csharp/Grpc.Core.Api/VersionInfo.cs
+++ b/src/csharp/Grpc.Core.Api/VersionInfo.cs
@@ -33,11 +33,11 @@ namespace Grpc.Core
         /// <summary>
         /// Current <c>AssemblyFileVersion</c> of gRPC C# assemblies
         /// </summary>
-        public const string CurrentAssemblyFileVersion = "1.21.0.0";
+        public const string CurrentAssemblyFileVersion = "1.22.0.0";
 
         /// <summary>
         /// Current version of gRPC C#
         /// </summary>
-        public const string CurrentVersion = "1.21.0-dev";
+        public const string CurrentVersion = "1.22.0-dev";
     }
 }
diff --git a/src/csharp/build/dependencies.props b/src/csharp/build/dependencies.props
index b018aac0f8e..dd5f172c27b 100644
--- a/src/csharp/build/dependencies.props
+++ b/src/csharp/build/dependencies.props
@@ -1,7 +1,7 @@
 <!-- This file is generated -->
 <Project>
   <PropertyGroup>
-    <GrpcCsharpVersion>1.21.0-dev</GrpcCsharpVersion>
+    <GrpcCsharpVersion>1.22.0-dev</GrpcCsharpVersion>
     <GoogleProtobufVersion>3.7.0</GoogleProtobufVersion>
   </PropertyGroup>
 </Project>
diff --git a/src/csharp/build_unitypackage.bat b/src/csharp/build_unitypackage.bat
index 8c7718f727f..2f4cd2739da 100644
--- a/src/csharp/build_unitypackage.bat
+++ b/src/csharp/build_unitypackage.bat
@@ -13,7 +13,7 @@
 @rem limitations under the License.
 
 @rem Current package versions
-set VERSION=1.21.0-dev
+set VERSION=1.22.0-dev
 
 @rem Adjust the location of nuget.exe
 set NUGET=C:\nuget\nuget.exe
diff --git a/src/objective-c/!ProtoCompiler-gRPCPlugin.podspec b/src/objective-c/!ProtoCompiler-gRPCPlugin.podspec
index 88b8d2975d6..401540209af 100644
--- a/src/objective-c/!ProtoCompiler-gRPCPlugin.podspec
+++ b/src/objective-c/!ProtoCompiler-gRPCPlugin.podspec
@@ -42,7 +42,7 @@ Pod::Spec.new do |s|
   # exclamation mark ensures that other "regular" pods will be able to find it as it'll be installed
   # before them.
   s.name     = '!ProtoCompiler-gRPCPlugin'
-  v = '1.21.0-dev'
+  v = '1.22.0-dev'
   s.version  = v
   s.summary  = 'The gRPC ProtoC plugin generates Objective-C files from .proto services.'
   s.description = <<-DESC
diff --git a/src/objective-c/GRPCClient/private/GRPCSecureChannelFactory.m b/src/objective-c/GRPCClient/private/GRPCSecureChannelFactory.m
index e6522d7a27e..7557367ed4a 100644
--- a/src/objective-c/GRPCClient/private/GRPCSecureChannelFactory.m
+++ b/src/objective-c/GRPCClient/private/GRPCSecureChannelFactory.m
@@ -61,7 +61,8 @@
     NSBundle *resourceBundle = [NSBundle
         bundleWithURL:[[bundle resourceURL] URLByAppendingPathComponent:resourceBundlePath]];
     NSString *path = [resourceBundle pathForResource:rootsPEM ofType:@"pem"];
-    setenv("GRPC_DEFAULT_SSL_ROOTS_FILE_PATH", [path cStringUsingEncoding:NSUTF8StringEncoding], 1);
+    setenv(GRPC_DEFAULT_SSL_ROOTS_FILE_PATH_ENV_VAR,
+           [path cStringUsingEncoding:NSUTF8StringEncoding], 1);
   });
 
   NSData *rootsASCII = nil;
diff --git a/src/objective-c/GRPCClient/private/version.h b/src/objective-c/GRPCClient/private/version.h
index fcbdfb21539..6fe0c396dd3 100644
--- a/src/objective-c/GRPCClient/private/version.h
+++ b/src/objective-c/GRPCClient/private/version.h
@@ -22,4 +22,4 @@
 // instead. This file can be regenerated from the template by running
 // `tools/buildgen/generate_projects.sh`.
 
-#define GRPC_OBJC_VERSION_STRING @"1.21.0-dev"
+#define GRPC_OBJC_VERSION_STRING @"1.22.0-dev"
diff --git a/src/objective-c/tests/CoreCronetEnd2EndTests/CoreCronetEnd2EndTests.mm b/src/objective-c/tests/CoreCronetEnd2EndTests/CoreCronetEnd2EndTests.mm
index 0d081e4a410..2fac1be3d0e 100644
--- a/src/objective-c/tests/CoreCronetEnd2EndTests/CoreCronetEnd2EndTests.mm
+++ b/src/objective-c/tests/CoreCronetEnd2EndTests/CoreCronetEnd2EndTests.mm
@@ -37,11 +37,11 @@
 #include <grpc/support/log.h>
 
 #include "src/core/lib/channel/channel_args.h"
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/host_port.h"
 #include "src/core/lib/gpr/string.h"
 #include "src/core/lib/gpr/tmpfile.h"
 #include "src/core/lib/security/credentials/credentials.h"
-#include "src/core/lib/security/security_connector/ssl_utils.h"
 #include "test/core/end2end/data/ssl_test_data.h"
 #include "test/core/util/port.h"
 #include "test/core/util/test_config.h"
@@ -172,7 +172,7 @@ static char *roots_filename;
   GPR_ASSERT(roots_file != NULL);
   GPR_ASSERT(fwrite(test_root_cert, 1, roots_size, roots_file) == roots_size);
   fclose(roots_file);
-  GPR_GLOBAL_CONFIG_SET(grpc_default_ssl_roots_file_path, roots_filename);
+  gpr_setenv(GRPC_DEFAULT_SSL_ROOTS_FILE_PATH_ENV_VAR, roots_filename);
 
   grpc_init();
 
diff --git a/src/objective-c/tests/version.h b/src/objective-c/tests/version.h
index 87516de11e8..c835c1da190 100644
--- a/src/objective-c/tests/version.h
+++ b/src/objective-c/tests/version.h
@@ -22,5 +22,5 @@
 // instead. This file can be regenerated from the template by running
 // `tools/buildgen/generate_projects.sh`.
 
-#define GRPC_OBJC_VERSION_STRING @"1.21.0-dev"
+#define GRPC_OBJC_VERSION_STRING @"1.22.0-dev"
 #define GRPC_C_VERSION_STRING @"7.0.0"
diff --git a/src/php/composer.json b/src/php/composer.json
index a9d0aebffca..ca1001b6d2b 100644
--- a/src/php/composer.json
+++ b/src/php/composer.json
@@ -2,7 +2,7 @@
   "name": "grpc/grpc-dev",
   "description": "gRPC library for PHP - for Developement use only",
   "license": "Apache-2.0",
-  "version": "1.21.0",
+  "version": "1.22.0",
   "require": {
     "php": ">=5.5.0",
     "google/protobuf": "^v3.3.0"
diff --git a/src/php/ext/grpc/version.h b/src/php/ext/grpc/version.h
index 43b3fa629ff..3e9f88c61d6 100644
--- a/src/php/ext/grpc/version.h
+++ b/src/php/ext/grpc/version.h
@@ -20,6 +20,6 @@
 #ifndef VERSION_H
 #define VERSION_H
 
-#define PHP_GRPC_VERSION "1.21.0dev"
+#define PHP_GRPC_VERSION "1.22.0dev"
 
 #endif /* VERSION_H */
diff --git a/src/python/grpcio/grpc/_grpcio_metadata.py b/src/python/grpcio/grpc/_grpcio_metadata.py
index 651f8f778f2..9f7ca9d5603 100644
--- a/src/python/grpcio/grpc/_grpcio_metadata.py
+++ b/src/python/grpcio/grpc/_grpcio_metadata.py
@@ -14,4 +14,4 @@
 
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/src/python/grpcio/grpc/_grpcio_metadata.py.template`!!!
 
-__version__ = """1.21.0.dev0"""
+__version__ = """1.22.0.dev0"""
diff --git a/src/python/grpcio/grpc_core_dependencies.py b/src/python/grpcio/grpc_core_dependencies.py
index 2619ccf9740..77753d7766c 100644
--- a/src/python/grpcio/grpc_core_dependencies.py
+++ b/src/python/grpcio/grpc_core_dependencies.py
@@ -385,7 +385,6 @@ CORE_SOURCE_FILES = [
     'src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_libuv.cc',
     'src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_posix.cc',
     'src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_windows.cc',
-    'src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.cc',
     'src/core/ext/filters/client_channel/resolver/dns/native/dns_resolver.cc',
     'src/core/ext/filters/client_channel/resolver/sockaddr/sockaddr_resolver.cc',
     'src/core/ext/filters/census/grpc_context.cc',
diff --git a/src/python/grpcio/grpc_version.py b/src/python/grpcio/grpc_version.py
index e430cc20a6d..971fd37afb6 100644
--- a/src/python/grpcio/grpc_version.py
+++ b/src/python/grpcio/grpc_version.py
@@ -14,4 +14,4 @@
 
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/src/python/grpcio/grpc_version.py.template`!!!
 
-VERSION = '1.21.0.dev0'
+VERSION = '1.22.0.dev0'
diff --git a/src/python/grpcio_channelz/grpc_version.py b/src/python/grpcio_channelz/grpc_version.py
index d716b953f4b..52baab4c30f 100644
--- a/src/python/grpcio_channelz/grpc_version.py
+++ b/src/python/grpcio_channelz/grpc_version.py
@@ -14,4 +14,4 @@
 
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/src/python/grpcio_channelz/grpc_version.py.template`!!!
 
-VERSION = '1.21.0.dev0'
+VERSION = '1.22.0.dev0'
diff --git a/src/python/grpcio_health_checking/grpc_version.py b/src/python/grpcio_health_checking/grpc_version.py
index 2bb47aaf133..be4ca841361 100644
--- a/src/python/grpcio_health_checking/grpc_version.py
+++ b/src/python/grpcio_health_checking/grpc_version.py
@@ -14,4 +14,4 @@
 
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/src/python/grpcio_health_checking/grpc_version.py.template`!!!
 
-VERSION = '1.21.0.dev0'
+VERSION = '1.22.0.dev0'
diff --git a/src/python/grpcio_reflection/grpc_version.py b/src/python/grpcio_reflection/grpc_version.py
index e1c4f3df694..1efc4ee2c8d 100644
--- a/src/python/grpcio_reflection/grpc_version.py
+++ b/src/python/grpcio_reflection/grpc_version.py
@@ -14,4 +14,4 @@
 
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/src/python/grpcio_reflection/grpc_version.py.template`!!!
 
-VERSION = '1.21.0.dev0'
+VERSION = '1.22.0.dev0'
diff --git a/src/python/grpcio_status/grpc_version.py b/src/python/grpcio_status/grpc_version.py
index b484a7ba478..9e443087755 100644
--- a/src/python/grpcio_status/grpc_version.py
+++ b/src/python/grpcio_status/grpc_version.py
@@ -14,4 +14,4 @@
 
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/src/python/grpcio_status/grpc_version.py.template`!!!
 
-VERSION = '1.21.0.dev0'
+VERSION = '1.22.0.dev0'
diff --git a/src/python/grpcio_testing/grpc_version.py b/src/python/grpcio_testing/grpc_version.py
index 21981ee79d2..18d17e40464 100644
--- a/src/python/grpcio_testing/grpc_version.py
+++ b/src/python/grpcio_testing/grpc_version.py
@@ -14,4 +14,4 @@
 
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/src/python/grpcio_testing/grpc_version.py.template`!!!
 
-VERSION = '1.21.0.dev0'
+VERSION = '1.22.0.dev0'
diff --git a/src/python/grpcio_tests/grpc_version.py b/src/python/grpcio_tests/grpc_version.py
index 8ce4fdb627d..401b0bd9697 100644
--- a/src/python/grpcio_tests/grpc_version.py
+++ b/src/python/grpcio_tests/grpc_version.py
@@ -14,4 +14,4 @@
 
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/src/python/grpcio_tests/grpc_version.py.template`!!!
 
-VERSION = '1.21.0.dev0'
+VERSION = '1.22.0.dev0'
diff --git a/src/ruby/ext/grpc/rb_grpc_imports.generated.h b/src/ruby/ext/grpc/rb_grpc_imports.generated.h
index 275ca6e9cbf..c25d789a95b 100644
--- a/src/ruby/ext/grpc/rb_grpc_imports.generated.h
+++ b/src/ruby/ext/grpc/rb_grpc_imports.generated.h
@@ -440,7 +440,7 @@ extern grpc_local_credentials_create_type grpc_local_credentials_create_import;
 typedef grpc_server_credentials*(*grpc_local_server_credentials_create_type)(grpc_local_connect_type type);
 extern grpc_local_server_credentials_create_type grpc_local_server_credentials_create_import;
 #define grpc_local_server_credentials_create grpc_local_server_credentials_create_import
-typedef grpc_tls_credentials_options*(*grpc_tls_credentials_options_create_type)();
+typedef grpc_tls_credentials_options*(*grpc_tls_credentials_options_create_type)(void);
 extern grpc_tls_credentials_options_create_type grpc_tls_credentials_options_create_import;
 #define grpc_tls_credentials_options_create grpc_tls_credentials_options_create_import
 typedef int(*grpc_tls_credentials_options_set_cert_request_type_type)(grpc_tls_credentials_options* options, grpc_ssl_client_certificate_request_type type);
@@ -455,7 +455,7 @@ extern grpc_tls_credentials_options_set_credential_reload_config_type grpc_tls_c
 typedef int(*grpc_tls_credentials_options_set_server_authorization_check_config_type)(grpc_tls_credentials_options* options, grpc_tls_server_authorization_check_config* config);
 extern grpc_tls_credentials_options_set_server_authorization_check_config_type grpc_tls_credentials_options_set_server_authorization_check_config_import;
 #define grpc_tls_credentials_options_set_server_authorization_check_config grpc_tls_credentials_options_set_server_authorization_check_config_import
-typedef grpc_tls_key_materials_config*(*grpc_tls_key_materials_config_create_type)();
+typedef grpc_tls_key_materials_config*(*grpc_tls_key_materials_config_create_type)(void);
 extern grpc_tls_key_materials_config_create_type grpc_tls_key_materials_config_create_import;
 #define grpc_tls_key_materials_config_create grpc_tls_key_materials_config_create_import
 typedef int(*grpc_tls_key_materials_config_set_key_materials_type)(grpc_tls_key_materials_config* config, const char* pem_root_certs, const grpc_ssl_pem_key_cert_pair** pem_key_cert_pairs, size_t num_key_cert_pairs);
diff --git a/src/ruby/lib/grpc/version.rb b/src/ruby/lib/grpc/version.rb
index cca795b64ec..75e6191216d 100644
--- a/src/ruby/lib/grpc/version.rb
+++ b/src/ruby/lib/grpc/version.rb
@@ -14,5 +14,5 @@
 
 # GRPC contains the General RPC module.
 module GRPC
-  VERSION = '1.21.0.dev'
+  VERSION = '1.22.0.dev'
 end
diff --git a/src/ruby/tools/version.rb b/src/ruby/tools/version.rb
index 5604e215b58..fbd0041fa35 100644
--- a/src/ruby/tools/version.rb
+++ b/src/ruby/tools/version.rb
@@ -14,6 +14,6 @@
 
 module GRPC
   module Tools
-    VERSION = '1.21.0.dev'
+    VERSION = '1.22.0.dev'
   end
 end
diff --git a/templates/tools/dockerfile/interoptest/grpc_interop_aspnetcore/build_interop.sh.template b/templates/tools/dockerfile/interoptest/grpc_interop_aspnetcore/build_interop.sh.template
index 05ad947e944..d64286ab03c 100644
--- a/templates/tools/dockerfile/interoptest/grpc_interop_aspnetcore/build_interop.sh.template
+++ b/templates/tools/dockerfile/interoptest/grpc_interop_aspnetcore/build_interop.sh.template
@@ -41,5 +41,4 @@
   
   ./build/get-grpc.sh
 
-  cd testassets/InteropTestsWebsite
-  dotnet build --configuration Debug
+  dotnet build --configuration Debug Grpc.AspNetCore.sln
diff --git a/test/core/bad_connection/close_fd_test.cc b/test/core/bad_connection/close_fd_test.cc
index 78a1a5cc9a4..e8f297e77ea 100644
--- a/test/core/bad_connection/close_fd_test.cc
+++ b/test/core/bad_connection/close_fd_test.cc
@@ -39,6 +39,7 @@
 #include <grpc/support/log.h>
 #include <grpc/support/time.h>
 #include "src/core/ext/transport/chttp2/transport/chttp2_transport.h"
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/iomgr/endpoint_pair.h"
 #include "src/core/lib/surface/channel.h"
 #include "src/core/lib/surface/completion_queue.h"
diff --git a/test/core/bad_ssl/bad_ssl_test.cc b/test/core/bad_ssl/bad_ssl_test.cc
index 8dd55f64944..73d251eff4a 100644
--- a/test/core/bad_ssl/bad_ssl_test.cc
+++ b/test/core/bad_ssl/bad_ssl_test.cc
@@ -25,9 +25,9 @@
 #include <grpc/support/log.h>
 #include <grpc/support/string_util.h>
 
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/host_port.h"
 #include "src/core/lib/gpr/string.h"
-#include "src/core/lib/security/security_connector/ssl_utils.h"
 #include "test/core/end2end/cq_verifier.h"
 #include "test/core/util/port.h"
 #include "test/core/util/subprocess.h"
@@ -133,7 +133,7 @@ int main(int argc, char** argv) {
     strcpy(root, ".");
   }
   if (argc == 2) {
-    GPR_GLOBAL_CONFIG_SET(grpc_default_ssl_roots_file_path, argv[1]);
+    gpr_setenv("GRPC_DEFAULT_SSL_ROOTS_FILE_PATH", argv[1]);
   }
   /* figure out our test name */
   tmp = lunder - 1;
diff --git a/test/core/client_channel/resolvers/dns_resolver_test.cc b/test/core/client_channel/resolvers/dns_resolver_test.cc
index 129866b7d7f..ed3b4e66472 100644
--- a/test/core/client_channel/resolvers/dns_resolver_test.cc
+++ b/test/core/client_channel/resolvers/dns_resolver_test.cc
@@ -21,8 +21,8 @@
 #include <grpc/support/log.h>
 
 #include "src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.h"
-#include "src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.h"
 #include "src/core/ext/filters/client_channel/resolver_registry.h"
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/string.h"
 #include "src/core/lib/iomgr/combiner.h"
 #include "test/core/util/test_config.h"
@@ -78,13 +78,13 @@ int main(int argc, char** argv) {
   test_succeeds(dns, "dns:10.2.1.1:1234");
   test_succeeds(dns, "dns:www.google.com");
   test_succeeds(dns, "dns:///www.google.com");
-  grpc_core::UniquePtr<char> resolver =
-      GPR_GLOBAL_CONFIG_GET(grpc_dns_resolver);
-  if (gpr_stricmp(resolver.get(), "native") == 0) {
+  char* resolver_env = gpr_getenv("GRPC_DNS_RESOLVER");
+  if (resolver_env != nullptr && gpr_stricmp(resolver_env, "native") == 0) {
     test_fails(dns, "dns://8.8.8.8/8.8.8.8:8888");
   } else {
     test_succeeds(dns, "dns://8.8.8.8/8.8.8.8:8888");
   }
+  gpr_free(resolver_env);
   {
     grpc_core::ExecCtx exec_ctx;
     GRPC_COMBINER_UNREF(g_combiner, "test");
diff --git a/test/core/end2end/fixtures/h2_full+trace.cc b/test/core/end2end/fixtures/h2_full+trace.cc
index b8dbe261183..ce8f6bf13a5 100644
--- a/test/core/end2end/fixtures/h2_full+trace.cc
+++ b/test/core/end2end/fixtures/h2_full+trace.cc
@@ -33,7 +33,7 @@
 #include "src/core/ext/filters/http/server/http_server_filter.h"
 #include "src/core/ext/transport/chttp2/transport/chttp2_transport.h"
 #include "src/core/lib/channel/connected_channel.h"
-#include "src/core/lib/debug/trace.h"
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/host_port.h"
 #include "src/core/lib/surface/channel.h"
 #include "src/core/lib/surface/server.h"
@@ -105,7 +105,7 @@ int main(int argc, char** argv) {
 
   /* force tracing on, with a value to force many
      code paths in trace.c to be taken */
-  GPR_GLOBAL_CONFIG_SET(grpc_trace, "doesnt-exist,http,all");
+  gpr_setenv("GRPC_TRACE", "doesnt-exist,http,all");
 
 #ifdef GRPC_POSIX_SOCKET
   g_fixture_slowdown_factor = isatty(STDOUT_FILENO) ? 10 : 1;
diff --git a/test/core/end2end/fixtures/h2_sockpair+trace.cc b/test/core/end2end/fixtures/h2_sockpair+trace.cc
index 7954bc1ddfc..4494d5c4746 100644
--- a/test/core/end2end/fixtures/h2_sockpair+trace.cc
+++ b/test/core/end2end/fixtures/h2_sockpair+trace.cc
@@ -35,7 +35,7 @@
 #include "src/core/ext/filters/http/server/http_server_filter.h"
 #include "src/core/ext/transport/chttp2/transport/chttp2_transport.h"
 #include "src/core/lib/channel/connected_channel.h"
-#include "src/core/lib/debug/trace.h"
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/iomgr/endpoint_pair.h"
 #include "src/core/lib/iomgr/iomgr.h"
 #include "src/core/lib/surface/channel.h"
@@ -133,8 +133,7 @@ int main(int argc, char** argv) {
 
   /* force tracing on, with a value to force many
      code paths in trace.c to be taken */
-  GPR_GLOBAL_CONFIG_SET(grpc_trace, "doesnt-exist,http,all");
-
+  gpr_setenv("GRPC_TRACE", "doesnt-exist,http,all");
 #ifdef GRPC_POSIX_SOCKET
   g_fixture_slowdown_factor = isatty(STDOUT_FILENO) ? 10 : 1;
 #else
diff --git a/test/core/end2end/fixtures/h2_spiffe.cc b/test/core/end2end/fixtures/h2_spiffe.cc
index cdf091bac10..9ab796ea429 100644
--- a/test/core/end2end/fixtures/h2_spiffe.cc
+++ b/test/core/end2end/fixtures/h2_spiffe.cc
@@ -35,7 +35,6 @@
 #include "src/core/lib/gprpp/thd.h"
 #include "src/core/lib/security/credentials/credentials.h"
 #include "src/core/lib/security/credentials/tls/grpc_tls_credentials_options.h"
-#include "src/core/lib/security/security_connector/ssl_utils.h"
 #include "test/core/end2end/data/ssl_test_data.h"
 #include "test/core/util/port.h"
 #include "test/core/util/test_config.h"
@@ -278,7 +277,7 @@ int main(int argc, char** argv) {
   GPR_ASSERT(roots_file != nullptr);
   GPR_ASSERT(fwrite(test_root_cert, 1, roots_size, roots_file) == roots_size);
   fclose(roots_file);
-  GPR_GLOBAL_CONFIG_SET(grpc_default_ssl_roots_file_path, roots_filename);
+  gpr_setenv(GRPC_DEFAULT_SSL_ROOTS_FILE_PATH_ENV_VAR, roots_filename);
   grpc_init();
   for (size_t ind = 0; ind < sizeof(configs) / sizeof(*configs); ind++) {
     grpc_end2end_tests(argc, argv, configs[ind]);
diff --git a/test/core/end2end/fixtures/h2_ssl.cc b/test/core/end2end/fixtures/h2_ssl.cc
index 3fc9bc7f329..1fcd785e251 100644
--- a/test/core/end2end/fixtures/h2_ssl.cc
+++ b/test/core/end2end/fixtures/h2_ssl.cc
@@ -25,11 +25,11 @@
 #include <grpc/support/log.h>
 
 #include "src/core/lib/channel/channel_args.h"
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/host_port.h"
 #include "src/core/lib/gpr/string.h"
 #include "src/core/lib/gpr/tmpfile.h"
 #include "src/core/lib/security/credentials/credentials.h"
-#include "src/core/lib/security/security_connector/ssl_utils.h"
 #include "test/core/end2end/data/ssl_test_data.h"
 #include "test/core/util/port.h"
 #include "test/core/util/test_config.h"
@@ -167,7 +167,7 @@ int main(int argc, char** argv) {
   GPR_ASSERT(roots_file != nullptr);
   GPR_ASSERT(fwrite(test_root_cert, 1, roots_size, roots_file) == roots_size);
   fclose(roots_file);
-  GPR_GLOBAL_CONFIG_SET(grpc_default_ssl_roots_file_path, roots_filename);
+  gpr_setenv(GRPC_DEFAULT_SSL_ROOTS_FILE_PATH_ENV_VAR, roots_filename);
 
   grpc_init();
 
diff --git a/test/core/end2end/fixtures/h2_ssl_cred_reload.cc b/test/core/end2end/fixtures/h2_ssl_cred_reload.cc
index 1d54a431364..04d876ce3cd 100644
--- a/test/core/end2end/fixtures/h2_ssl_cred_reload.cc
+++ b/test/core/end2end/fixtures/h2_ssl_cred_reload.cc
@@ -25,11 +25,11 @@
 #include <grpc/support/log.h>
 
 #include "src/core/lib/channel/channel_args.h"
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/host_port.h"
 #include "src/core/lib/gpr/string.h"
 #include "src/core/lib/gpr/tmpfile.h"
 #include "src/core/lib/security/credentials/credentials.h"
-#include "src/core/lib/security/security_connector/ssl_utils.h"
 #include "test/core/end2end/data/ssl_test_data.h"
 #include "test/core/util/port.h"
 #include "test/core/util/test_config.h"
@@ -190,7 +190,7 @@ int main(int argc, char** argv) {
   GPR_ASSERT(roots_file != nullptr);
   GPR_ASSERT(fwrite(test_root_cert, 1, roots_size, roots_file) == roots_size);
   fclose(roots_file);
-  GPR_GLOBAL_CONFIG_SET(grpc_default_ssl_roots_file_path, roots_filename);
+  gpr_setenv(GRPC_DEFAULT_SSL_ROOTS_FILE_PATH_ENV_VAR, roots_filename);
 
   grpc_init();
 
diff --git a/test/core/end2end/fixtures/h2_ssl_proxy.cc b/test/core/end2end/fixtures/h2_ssl_proxy.cc
index d5f695b1575..f1858079426 100644
--- a/test/core/end2end/fixtures/h2_ssl_proxy.cc
+++ b/test/core/end2end/fixtures/h2_ssl_proxy.cc
@@ -25,11 +25,11 @@
 #include <grpc/support/log.h>
 
 #include "src/core/lib/channel/channel_args.h"
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/host_port.h"
 #include "src/core/lib/gpr/string.h"
 #include "src/core/lib/gpr/tmpfile.h"
 #include "src/core/lib/security/credentials/credentials.h"
-#include "src/core/lib/security/security_connector/ssl_utils.h"
 #include "test/core/end2end/data/ssl_test_data.h"
 #include "test/core/end2end/fixtures/proxy.h"
 #include "test/core/util/port.h"
@@ -208,7 +208,7 @@ int main(int argc, char** argv) {
   GPR_ASSERT(roots_file != nullptr);
   GPR_ASSERT(fwrite(test_root_cert, 1, roots_size, roots_file) == roots_size);
   fclose(roots_file);
-  GPR_GLOBAL_CONFIG_SET(grpc_default_ssl_roots_file_path, roots_filename);
+  gpr_setenv(GRPC_DEFAULT_SSL_ROOTS_FILE_PATH_ENV_VAR, roots_filename);
 
   grpc_init();
 
diff --git a/test/core/end2end/h2_ssl_cert_test.cc b/test/core/end2end/h2_ssl_cert_test.cc
index e9285778a2d..cb0800bf899 100644
--- a/test/core/end2end/h2_ssl_cert_test.cc
+++ b/test/core/end2end/h2_ssl_cert_test.cc
@@ -25,11 +25,11 @@
 #include <grpc/support/log.h>
 
 #include "src/core/lib/channel/channel_args.h"
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/host_port.h"
 #include "src/core/lib/gpr/string.h"
 #include "src/core/lib/gpr/tmpfile.h"
 #include "src/core/lib/security/credentials/credentials.h"
-#include "src/core/lib/security/security_connector/ssl_utils.h"
 #include "test/core/end2end/cq_verifier.h"
 #include "test/core/end2end/data/ssl_test_data.h"
 #include "test/core/util/port.h"
@@ -366,7 +366,7 @@ int main(int argc, char** argv) {
   GPR_ASSERT(roots_file != nullptr);
   GPR_ASSERT(fwrite(test_root_cert, 1, roots_size, roots_file) == roots_size);
   fclose(roots_file);
-  GPR_GLOBAL_CONFIG_SET(grpc_default_ssl_roots_file_path, roots_filename);
+  gpr_setenv(GRPC_DEFAULT_SSL_ROOTS_FILE_PATH_ENV_VAR, roots_filename);
 
   grpc_init();
   ::testing::InitGoogleTest(&argc, argv);
diff --git a/test/core/end2end/h2_ssl_session_reuse_test.cc b/test/core/end2end/h2_ssl_session_reuse_test.cc
index b2d0a5e1133..fbcdcc4b3f3 100644
--- a/test/core/end2end/h2_ssl_session_reuse_test.cc
+++ b/test/core/end2end/h2_ssl_session_reuse_test.cc
@@ -25,11 +25,11 @@
 #include <grpc/support/log.h>
 
 #include "src/core/lib/channel/channel_args.h"
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/host_port.h"
 #include "src/core/lib/gpr/string.h"
 #include "src/core/lib/gpr/tmpfile.h"
 #include "src/core/lib/security/credentials/credentials.h"
-#include "src/core/lib/security/security_connector/ssl_utils.h"
 #include "test/core/end2end/cq_verifier.h"
 #include "test/core/end2end/data/ssl_test_data.h"
 #include "test/core/util/port.h"
@@ -265,7 +265,7 @@ int main(int argc, char** argv) {
   GPR_ASSERT(roots_file != nullptr);
   GPR_ASSERT(fwrite(test_root_cert, 1, roots_size, roots_file) == roots_size);
   fclose(roots_file);
-  GPR_GLOBAL_CONFIG_SET(grpc_default_ssl_roots_file_path, roots_filename);
+  gpr_setenv(GRPC_DEFAULT_SSL_ROOTS_FILE_PATH_ENV_VAR, roots_filename);
 
   grpc_init();
   ::testing::InitGoogleTest(&argc, argv);
diff --git a/test/core/end2end/tests/keepalive_timeout.cc b/test/core/end2end/tests/keepalive_timeout.cc
index 1750f6fe5ee..3c33f0419ad 100644
--- a/test/core/end2end/tests/keepalive_timeout.cc
+++ b/test/core/end2end/tests/keepalive_timeout.cc
@@ -28,15 +28,11 @@
 
 #include "src/core/ext/transport/chttp2/transport/frame_ping.h"
 #include "src/core/lib/channel/channel_args.h"
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/useful.h"
 #include "src/core/lib/iomgr/exec_ctx.h"
-#include "src/core/lib/iomgr/iomgr.h"
 #include "test/core/end2end/cq_verifier.h"
 
-#ifdef GRPC_POSIX_SOCKET
-#include "src/core/lib/iomgr/ev_posix.h"
-#endif  // GRPC_POSIX_SOCKET
-
 static void* tag(intptr_t t) { return (void*)t; }
 
 static grpc_end2end_test_fixture begin_test(grpc_end2end_test_config config,
@@ -229,13 +225,13 @@ static void test_keepalive_timeout(grpc_end2end_test_config config) {
  * 200ms. In the success case, each ping ack should reset the keepalive timer so
  * that the keepalive ping is never sent. */
 static void test_read_delays_keepalive(grpc_end2end_test_config config) {
-#ifdef GRPC_POSIX_SOCKET
-  grpc_core::UniquePtr<char> poller = GPR_GLOBAL_CONFIG_GET(grpc_poll_strategy);
+  char* poller = gpr_getenv("GRPC_POLL_STRATEGY");
   /* It is hard to get the timing right for the polling engine poll. */
-  if ((0 == strcmp(poller.get(), "poll"))) {
+  if (poller != nullptr && (0 == strcmp(poller, "poll"))) {
+    gpr_free(poller);
     return;
   }
-#endif  // GRPC_POSIX_SOCKET
+  gpr_free(poller);
   const int kPingIntervalMS = 100;
   grpc_arg keepalive_arg_elems[3];
   keepalive_arg_elems[0].type = GRPC_ARG_INTEGER;
diff --git a/test/core/gpr/log_test.cc b/test/core/gpr/log_test.cc
index e320daa33a7..f96257738b2 100644
--- a/test/core/gpr/log_test.cc
+++ b/test/core/gpr/log_test.cc
@@ -21,14 +21,9 @@
 #include <stdbool.h>
 #include <string.h>
 
-#include "src/core/lib/gprpp/global_config.h"
+#include "src/core/lib/gpr/env.h"
 #include "test/core/util/test_config.h"
 
-// Config declaration is supposed to be located at log.h but
-// log.h doesn't include global_config headers because it has to
-// be a strict C so declaration statement gets to be here.
-GPR_GLOBAL_CONFIG_DECLARE_STRING(grpc_verbosity);
-
 static bool log_func_reached = false;
 
 static void test_callback(gpr_log_func_args* args) {
@@ -72,7 +67,7 @@ int main(int argc, char** argv) {
 
   /* gpr_log_verbosity_init() will be effective only once, and only before
    * gpr_set_log_verbosity() is called */
-  GPR_GLOBAL_CONFIG_SET(grpc_verbosity, "ERROR");
+  gpr_setenv("GRPC_VERBOSITY", "ERROR");
   gpr_log_verbosity_init();
 
   test_log_function_reached(GPR_ERROR);
@@ -80,7 +75,7 @@ int main(int argc, char** argv) {
   test_log_function_unreached(GPR_DEBUG);
 
   /* gpr_log_verbosity_init() should not be effective */
-  GPR_GLOBAL_CONFIG_SET(grpc_verbosity, "DEBUG");
+  gpr_setenv("GRPC_VERBOSITY", "DEBUG");
   gpr_log_verbosity_init();
   test_log_function_reached(GPR_ERROR);
   test_log_function_unreached(GPR_INFO);
@@ -102,7 +97,7 @@ int main(int argc, char** argv) {
   test_log_function_unreached(GPR_DEBUG);
 
   /* gpr_log_verbosity_init() should not be effective */
-  GPR_GLOBAL_CONFIG_SET(grpc_verbosity, "DEBUG");
+  gpr_setenv("GRPC_VERBOSITY", "DEBUG");
   gpr_log_verbosity_init();
   test_log_function_reached(GPR_ERROR);
   test_log_function_unreached(GPR_INFO);
diff --git a/test/core/http/httpscli_test.cc b/test/core/http/httpscli_test.cc
index e7250c206d8..326b0e95e25 100644
--- a/test/core/http/httpscli_test.cc
+++ b/test/core/http/httpscli_test.cc
@@ -29,7 +29,6 @@
 
 #include "src/core/lib/gpr/env.h"
 #include "src/core/lib/iomgr/iomgr.h"
-#include "src/core/lib/security/security_connector/ssl_utils.h"
 #include "test/core/util/port.h"
 #include "test/core/util/subprocess.h"
 #include "test/core/util/test_config.h"
@@ -185,7 +184,7 @@ int main(int argc, char** argv) {
   /* Set the environment variable for the SSL certificate file */
   char* pem_file;
   gpr_asprintf(&pem_file, "%s/src/core/tsi/test_creds/ca.pem", root);
-  GPR_GLOBAL_CONFIG_SET(grpc_default_ssl_roots_file_path, pem_file);
+  gpr_setenv(GRPC_DEFAULT_SSL_ROOTS_FILE_PATH_ENV_VAR, pem_file);
   gpr_free(pem_file);
 
   /* start the server */
diff --git a/test/core/iomgr/resolve_address_posix_test.cc b/test/core/iomgr/resolve_address_posix_test.cc
index 112d7c2791b..826c7e1fafa 100644
--- a/test/core/iomgr/resolve_address_posix_test.cc
+++ b/test/core/iomgr/resolve_address_posix_test.cc
@@ -29,7 +29,6 @@
 #include <grpc/support/sync.h>
 #include <grpc/support/time.h>
 
-#include "src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.h"
 #include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/string.h"
 #include "src/core/lib/gpr/useful.h"
@@ -225,16 +224,15 @@ int main(int argc, char** argv) {
   // --resolver will always be the first one, so only parse the first argument
   // (other arguments may be unknown to cl)
   gpr_cmdline_parse(cl, argc > 2 ? 2 : argc, argv);
-  grpc_core::UniquePtr<char> resolver =
-      GPR_GLOBAL_CONFIG_GET(grpc_dns_resolver);
-  if (strlen(resolver.get()) != 0) {
+  const char* cur_resolver = gpr_getenv("GRPC_DNS_RESOLVER");
+  if (cur_resolver != nullptr && strlen(cur_resolver) != 0) {
     gpr_log(GPR_INFO, "Warning: overriding resolver setting of %s",
-            resolver.get());
+            cur_resolver);
   }
   if (gpr_stricmp(resolver_type, "native") == 0) {
-    GPR_GLOBAL_CONFIG_SET(grpc_dns_resolver, "native");
+    gpr_setenv("GRPC_DNS_RESOLVER", "native");
   } else if (gpr_stricmp(resolver_type, "ares") == 0) {
-    GPR_GLOBAL_CONFIG_SET(grpc_dns_resolver, "ares");
+    gpr_setenv("GRPC_DNS_RESOLVER", "ares");
   } else {
     gpr_log(GPR_ERROR, "--resolver_type was not set to ares or native");
     abort();
@@ -248,12 +246,12 @@ int main(int argc, char** argv) {
     // c-ares resolver doesn't support UDS (ability for native DNS resolver
     // to handle this is only expected to be used by servers, which
     // unconditionally use the native DNS resolver).
-    grpc_core::UniquePtr<char> resolver =
-        GPR_GLOBAL_CONFIG_GET(grpc_dns_resolver);
-    if (gpr_stricmp(resolver.get(), "native") == 0) {
+    char* resolver_env = gpr_getenv("GRPC_DNS_RESOLVER");
+    if (resolver_env == nullptr || gpr_stricmp(resolver_env, "native") == 0) {
       test_unix_socket();
       test_unix_socket_path_name_too_long();
     }
+    gpr_free(resolver_env);
   }
   gpr_cmdline_destroy(cl);
 
diff --git a/test/core/iomgr/resolve_address_test.cc b/test/core/iomgr/resolve_address_test.cc
index cbc03485d7f..1f0c0e3e835 100644
--- a/test/core/iomgr/resolve_address_test.cc
+++ b/test/core/iomgr/resolve_address_test.cc
@@ -27,7 +27,7 @@
 
 #include <string.h>
 
-#include "src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.h"
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/string.h"
 #include "src/core/lib/iomgr/executor.h"
 #include "src/core/lib/iomgr/iomgr.h"
@@ -347,17 +347,16 @@ int main(int argc, char** argv) {
   // --resolver will always be the first one, so only parse the first argument
   // (other arguments may be unknown to cl)
   gpr_cmdline_parse(cl, argc > 2 ? 2 : argc, argv);
-  grpc_core::UniquePtr<char> resolver =
-      GPR_GLOBAL_CONFIG_GET(grpc_dns_resolver);
-  if (strlen(resolver.get()) != 0) {
+  const char* cur_resolver = gpr_getenv("GRPC_DNS_RESOLVER");
+  if (cur_resolver != nullptr && strlen(cur_resolver) != 0) {
     gpr_log(GPR_INFO, "Warning: overriding resolver setting of %s",
-            resolver.get());
+            cur_resolver);
   }
   if (gpr_stricmp(resolver_type, "native") == 0) {
-    GPR_GLOBAL_CONFIG_SET(grpc_dns_resolver, "native");
+    gpr_setenv("GRPC_DNS_RESOLVER", "native");
   } else if (gpr_stricmp(resolver_type, "ares") == 0) {
 #ifndef GRPC_UV
-    GPR_GLOBAL_CONFIG_SET(grpc_dns_resolver, "ares");
+    gpr_setenv("GRPC_DNS_RESOLVER", "ares");
 #endif
   } else {
     gpr_log(GPR_ERROR, "--resolver_type was not set to ares or native");
diff --git a/test/core/security/credentials_test.cc b/test/core/security/credentials_test.cc
index 141346bca94..11cfc8cc905 100644
--- a/test/core/security/credentials_test.cc
+++ b/test/core/security/credentials_test.cc
@@ -1161,7 +1161,7 @@ static void test_get_well_known_google_credentials_file_path(void) {
   GPR_ASSERT(path != nullptr);
   gpr_free(path);
 #if defined(GPR_POSIX_ENV) || defined(GPR_LINUX_ENV)
-  gpr_unsetenv("HOME");
+  unsetenv("HOME");
   path = grpc_get_well_known_google_credentials_file_path();
   GPR_ASSERT(path == nullptr);
   gpr_setenv("HOME", home);
diff --git a/test/core/security/security_connector_test.cc b/test/core/security/security_connector_test.cc
index c888c90c646..496f064439c 100644
--- a/test/core/security/security_connector_test.cc
+++ b/test/core/security/security_connector_test.cc
@@ -24,6 +24,7 @@
 #include <grpc/support/log.h>
 #include <grpc/support/string_util.h>
 
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/string.h"
 #include "src/core/lib/gpr/tmpfile.h"
 #include "src/core/lib/gprpp/ref_counted_ptr.h"
@@ -393,7 +394,7 @@ static void test_default_ssl_roots(void) {
 
   /* First let's get the root through the override: set the env to an invalid
      value. */
-  GPR_GLOBAL_CONFIG_SET(grpc_default_ssl_roots_file_path, "");
+  gpr_setenv(GRPC_DEFAULT_SSL_ROOTS_FILE_PATH_ENV_VAR, "");
   grpc_set_ssl_roots_override_callback(override_roots_success);
   grpc_slice roots =
       grpc_core::TestDefaultSslRootStore::ComputePemRootCertsForTesting();
@@ -404,8 +405,7 @@ static void test_default_ssl_roots(void) {
 
   /* Now let's set the env var: We should get the contents pointed value
      instead. */
-  GPR_GLOBAL_CONFIG_SET(grpc_default_ssl_roots_file_path,
-                        roots_env_var_file_path);
+  gpr_setenv(GRPC_DEFAULT_SSL_ROOTS_FILE_PATH_ENV_VAR, roots_env_var_file_path);
   roots = grpc_core::TestDefaultSslRootStore::ComputePemRootCertsForTesting();
   roots_contents = grpc_slice_to_c_string(roots);
   grpc_slice_unref(roots);
@@ -414,7 +414,7 @@ static void test_default_ssl_roots(void) {
 
   /* Now reset the env var. We should fall back to the value overridden using
      the api. */
-  GPR_GLOBAL_CONFIG_SET(grpc_default_ssl_roots_file_path, "");
+  gpr_setenv(GRPC_DEFAULT_SSL_ROOTS_FILE_PATH_ENV_VAR, "");
   roots = grpc_core::TestDefaultSslRootStore::ComputePemRootCertsForTesting();
   roots_contents = grpc_slice_to_c_string(roots);
   grpc_slice_unref(roots);
@@ -423,7 +423,7 @@ static void test_default_ssl_roots(void) {
 
   /* Now setup a permanent failure for the overridden roots and we should get
      an empty slice. */
-  GPR_GLOBAL_CONFIG_SET(grpc_not_use_system_ssl_roots, true);
+  gpr_setenv("GRPC_NOT_USE_SYSTEM_SSL_ROOTS", "true");
   grpc_set_ssl_roots_override_callback(override_roots_permanent_failure);
   roots = grpc_core::TestDefaultSslRootStore::ComputePemRootCertsForTesting();
   GPR_ASSERT(GRPC_SLICE_IS_EMPTY(roots));
diff --git a/test/core/slice/slice_buffer_test.cc b/test/core/slice/slice_buffer_test.cc
index b53e3312df1..7d4acfed003 100644
--- a/test/core/slice/slice_buffer_test.cc
+++ b/test/core/slice/slice_buffer_test.cc
@@ -19,6 +19,7 @@
 #include <grpc/grpc.h>
 #include <grpc/slice_buffer.h>
 #include <grpc/support/log.h>
+#include "src/core/lib/slice/slice_internal.h"
 #include "test/core/util/test_config.h"
 
 void test_slice_buffer_add() {
@@ -105,12 +106,54 @@ void test_slice_buffer_move_first() {
   GPR_ASSERT(dst.length == dst_len);
 }
 
+void test_slice_buffer_first() {
+  grpc_slice slices[3];
+  slices[0] = grpc_slice_from_copied_string("aaa");
+  slices[1] = grpc_slice_from_copied_string("bbbb");
+  slices[2] = grpc_slice_from_copied_string("ccccc");
+
+  grpc_slice_buffer buf;
+  grpc_slice_buffer_init(&buf);
+  for (int idx = 0; idx < 3; ++idx) {
+    grpc_slice_ref(slices[idx]);
+    grpc_slice_buffer_add_indexed(&buf, slices[idx]);
+  }
+
+  grpc_slice* first = grpc_slice_buffer_peek_first(&buf);
+  GPR_ASSERT(GPR_SLICE_LENGTH(*first) == GPR_SLICE_LENGTH(slices[0]));
+  GPR_ASSERT(buf.count == 3);
+  GPR_ASSERT(buf.length == 12);
+
+  grpc_slice_buffer_sub_first(&buf, 1, 2);
+  first = grpc_slice_buffer_peek_first(&buf);
+  GPR_ASSERT(GPR_SLICE_LENGTH(*first) == 1);
+  GPR_ASSERT(buf.count == 3);
+  GPR_ASSERT(buf.length == 10);
+
+  grpc_slice_buffer_remove_first(&buf);
+  first = grpc_slice_buffer_peek_first(&buf);
+  GPR_ASSERT(GPR_SLICE_LENGTH(*first) == GPR_SLICE_LENGTH(slices[1]));
+  GPR_ASSERT(buf.count == 2);
+  GPR_ASSERT(buf.length == 9);
+
+  grpc_slice_buffer_remove_first(&buf);
+  first = grpc_slice_buffer_peek_first(&buf);
+  GPR_ASSERT(GPR_SLICE_LENGTH(*first) == GPR_SLICE_LENGTH(slices[2]));
+  GPR_ASSERT(buf.count == 1);
+  GPR_ASSERT(buf.length == 5);
+
+  grpc_slice_buffer_remove_first(&buf);
+  GPR_ASSERT(buf.count == 0);
+  GPR_ASSERT(buf.length == 0);
+}
+
 int main(int argc, char** argv) {
   grpc::testing::TestEnvironment env(argc, argv);
   grpc_init();
 
   test_slice_buffer_add();
   test_slice_buffer_move_first();
+  test_slice_buffer_first();
 
   grpc_shutdown();
   return 0;
diff --git a/test/core/util/test_config.cc b/test/core/util/test_config.cc
index 5b248a01daa..476e424b1eb 100644
--- a/test/core/util/test_config.cc
+++ b/test/core/util/test_config.cc
@@ -28,6 +28,7 @@
 #include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
 
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/string.h"
 #include "src/core/lib/gpr/useful.h"
 #include "src/core/lib/surface/init.h"
diff --git a/test/cpp/end2end/async_end2end_test.cc b/test/cpp/end2end/async_end2end_test.cc
index 6ca0edf123e..97275db6276 100644
--- a/test/cpp/end2end/async_end2end_test.cc
+++ b/test/cpp/end2end/async_end2end_test.cc
@@ -33,6 +33,7 @@
 #include <grpcpp/server_context.h>
 
 #include "src/core/ext/filters/client_channel/backup_poller.h"
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/tls.h"
 #include "src/core/lib/iomgr/port.h"
 #include "src/proto/grpc/health/v1/health.grpc.pb.h"
@@ -43,10 +44,6 @@
 #include "test/cpp/util/string_ref_helper.h"
 #include "test/cpp/util/test_credentials_provider.h"
 
-#ifdef GRPC_POSIX_SOCKET
-#include "src/core/lib/iomgr/ev_posix.h"
-#endif  // GRPC_POSIX_SOCKET
-
 #include <gtest/gtest.h>
 
 using grpc::testing::EchoRequest;
@@ -362,14 +359,13 @@ TEST_P(AsyncEnd2endTest, ReconnectChannel) {
     return;
   }
   int poller_slowdown_factor = 1;
-#ifdef GRPC_POSIX_SOCKET
   // It needs 2 pollset_works to reconnect the channel with polling engine
   // "poll"
-  grpc_core::UniquePtr<char> poller = GPR_GLOBAL_CONFIG_GET(grpc_poll_strategy);
-  if (0 == strcmp(poller.get(), "poll")) {
+  char* s = gpr_getenv("GRPC_POLL_STRATEGY");
+  if (s != nullptr && 0 == strcmp(s, "poll")) {
     poller_slowdown_factor = 2;
   }
-#endif  // GRPC_POSIX_SOCKET
+  gpr_free(s);
   ResetStub();
   SendRpc(1);
   server_->Shutdown();
diff --git a/test/cpp/end2end/client_lb_end2end_test.cc b/test/cpp/end2end/client_lb_end2end_test.cc
index 766c38a64a1..b623348e13f 100644
--- a/test/cpp/end2end/client_lb_end2end_test.cc
+++ b/test/cpp/end2end/client_lb_end2end_test.cc
@@ -1019,8 +1019,8 @@ TEST_F(ClientLbEnd2endTest, RoundRobinUpdates) {
   auto channel = BuildChannel("round_robin");
   auto stub = BuildStub(channel);
   std::vector<int> ports;
-
   // Start with a single server.
+  gpr_log(GPR_INFO, "*** FIRST BACKEND ***");
   ports.emplace_back(servers_[0]->port_);
   SetNextResolution(ports);
   WaitForServer(stub, 0, DEBUG_LOCATION);
@@ -1030,36 +1030,33 @@ TEST_F(ClientLbEnd2endTest, RoundRobinUpdates) {
   EXPECT_EQ(0, servers_[1]->service_.request_count());
   EXPECT_EQ(0, servers_[2]->service_.request_count());
   servers_[0]->service_.ResetCounters();
-
   // And now for the second server.
+  gpr_log(GPR_INFO, "*** SECOND BACKEND ***");
   ports.clear();
   ports.emplace_back(servers_[1]->port_);
   SetNextResolution(ports);
-
   // Wait until update has been processed, as signaled by the second backend
   // receiving a request.
   EXPECT_EQ(0, servers_[1]->service_.request_count());
   WaitForServer(stub, 1, DEBUG_LOCATION);
-
   for (size_t i = 0; i < 10; ++i) CheckRpcSendOk(stub, DEBUG_LOCATION);
   EXPECT_EQ(0, servers_[0]->service_.request_count());
   EXPECT_EQ(10, servers_[1]->service_.request_count());
   EXPECT_EQ(0, servers_[2]->service_.request_count());
   servers_[1]->service_.ResetCounters();
-
   // ... and for the last server.
+  gpr_log(GPR_INFO, "*** THIRD BACKEND ***");
   ports.clear();
   ports.emplace_back(servers_[2]->port_);
   SetNextResolution(ports);
   WaitForServer(stub, 2, DEBUG_LOCATION);
-
   for (size_t i = 0; i < 10; ++i) CheckRpcSendOk(stub, DEBUG_LOCATION);
   EXPECT_EQ(0, servers_[0]->service_.request_count());
   EXPECT_EQ(0, servers_[1]->service_.request_count());
   EXPECT_EQ(10, servers_[2]->service_.request_count());
   servers_[2]->service_.ResetCounters();
-
   // Back to all servers.
+  gpr_log(GPR_INFO, "*** ALL BACKENDS ***");
   ports.clear();
   ports.emplace_back(servers_[0]->port_);
   ports.emplace_back(servers_[1]->port_);
@@ -1068,14 +1065,13 @@ TEST_F(ClientLbEnd2endTest, RoundRobinUpdates) {
   WaitForServer(stub, 0, DEBUG_LOCATION);
   WaitForServer(stub, 1, DEBUG_LOCATION);
   WaitForServer(stub, 2, DEBUG_LOCATION);
-
   // Send three RPCs, one per server.
   for (size_t i = 0; i < 3; ++i) CheckRpcSendOk(stub, DEBUG_LOCATION);
   EXPECT_EQ(1, servers_[0]->service_.request_count());
   EXPECT_EQ(1, servers_[1]->service_.request_count());
   EXPECT_EQ(1, servers_[2]->service_.request_count());
-
   // An empty update will result in the channel going into TRANSIENT_FAILURE.
+  gpr_log(GPR_INFO, "*** NO BACKENDS ***");
   ports.clear();
   SetNextResolution(ports);
   grpc_connectivity_state channel_state;
@@ -1084,15 +1080,14 @@ TEST_F(ClientLbEnd2endTest, RoundRobinUpdates) {
   } while (channel_state == GRPC_CHANNEL_READY);
   ASSERT_NE(channel_state, GRPC_CHANNEL_READY);
   servers_[0]->service_.ResetCounters();
-
   // Next update introduces servers_[1], making the channel recover.
+  gpr_log(GPR_INFO, "*** BACK TO SECOND BACKEND ***");
   ports.clear();
   ports.emplace_back(servers_[1]->port_);
   SetNextResolution(ports);
   WaitForServer(stub, 1, DEBUG_LOCATION);
   channel_state = channel->GetState(false /* try to connect */);
   ASSERT_EQ(channel_state, GRPC_CHANNEL_READY);
-
   // Check LB policy name for the channel.
   EXPECT_EQ("round_robin", channel->GetLoadBalancingPolicyName());
 }
@@ -1211,8 +1206,9 @@ TEST_F(ClientLbEnd2endTest, RoundRobinSingleReconnect) {
   auto channel = BuildChannel("round_robin");
   auto stub = BuildStub(channel);
   SetNextResolution(ports);
-  for (size_t i = 0; i < kNumServers; ++i)
+  for (size_t i = 0; i < kNumServers; ++i) {
     WaitForServer(stub, i, DEBUG_LOCATION);
+  }
   for (size_t i = 0; i < servers_.size(); ++i) {
     CheckRpcSendOk(stub, DEBUG_LOCATION);
     EXPECT_EQ(1, servers_[i]->service_.request_count()) << "for backend #" << i;
@@ -1236,7 +1232,6 @@ TEST_F(ClientLbEnd2endTest, RoundRobinSingleReconnect) {
   // No requests have gone to the deceased server.
   EXPECT_EQ(pre_death, post_death);
   // Bring the first server back up.
-  servers_[0].reset(new ServerData(ports[0]));
   StartServer(0);
   // Requests should start arriving at the first server either right away (if
   // the server managed to start before the RR policy retried the subchannel) or
@@ -1360,6 +1355,52 @@ TEST_F(ClientLbEnd2endTest, RoundRobinWithHealthCheckingInhibitPerChannel) {
   // Second channel should be READY.
   EXPECT_TRUE(WaitForChannelReady(channel2.get(), 1));
   CheckRpcSendOk(stub2, DEBUG_LOCATION);
+  // Enable health checks on the backend and wait for channel 1 to succeed.
+  servers_[0]->SetServingStatus("health_check_service_name", true);
+  CheckRpcSendOk(stub1, DEBUG_LOCATION, true /* wait_for_ready */);
+  // Check that we created only one subchannel to the backend.
+  EXPECT_EQ(1UL, servers_[0]->service_.clients().size());
+  // Clean up.
+  EnableDefaultHealthCheckService(false);
+}
+
+TEST_F(ClientLbEnd2endTest, RoundRobinWithHealthCheckingServiceNamePerChannel) {
+  EnableDefaultHealthCheckService(true);
+  // Start server.
+  const int kNumServers = 1;
+  StartServers(kNumServers);
+  // Create a channel with health-checking enabled.
+  ChannelArguments args;
+  args.SetServiceConfigJSON(
+      "{\"healthCheckConfig\": "
+      "{\"serviceName\": \"health_check_service_name\"}}");
+  auto channel1 = BuildChannel("round_robin", args);
+  auto stub1 = BuildStub(channel1);
+  std::vector<int> ports = GetServersPorts();
+  SetNextResolution(ports);
+  // Create a channel with health-checking enabled with a different
+  // service name.
+  ChannelArguments args2;
+  args2.SetServiceConfigJSON(
+      "{\"healthCheckConfig\": "
+      "{\"serviceName\": \"health_check_service_name2\"}}");
+  auto channel2 = BuildChannel("round_robin", args2);
+  auto stub2 = BuildStub(channel2);
+  SetNextResolution(ports);
+  // Allow health checks from channel 2 to succeed.
+  servers_[0]->SetServingStatus("health_check_service_name2", true);
+  // First channel should not become READY, because health checks should be
+  // failing.
+  EXPECT_FALSE(WaitForChannelReady(channel1.get(), 1));
+  CheckRpcSendFailure(stub1);
+  // Second channel should be READY.
+  EXPECT_TRUE(WaitForChannelReady(channel2.get(), 1));
+  CheckRpcSendOk(stub2, DEBUG_LOCATION);
+  // Enable health checks for channel 1 and wait for it to succeed.
+  servers_[0]->SetServingStatus("health_check_service_name", true);
+  CheckRpcSendOk(stub1, DEBUG_LOCATION, true /* wait_for_ready */);
+  // Check that we created only one subchannel to the backend.
+  EXPECT_EQ(1UL, servers_[0]->service_.clients().size());
   // Clean up.
   EnableDefaultHealthCheckService(false);
 }
diff --git a/test/cpp/end2end/end2end_test.cc b/test/cpp/end2end/end2end_test.cc
index 8fae2da217f..e5dc88ae6d7 100644
--- a/test/cpp/end2end/end2end_test.cc
+++ b/test/cpp/end2end/end2end_test.cc
@@ -35,6 +35,7 @@
 #include <grpcpp/server_context.h>
 
 #include "src/core/ext/filters/client_channel/backup_poller.h"
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/iomgr/iomgr.h"
 #include "src/core/lib/security/credentials/credentials.h"
 #include "src/proto/grpc/testing/duplicate/echo_duplicate.grpc.pb.h"
@@ -46,10 +47,6 @@
 #include "test/cpp/util/string_ref_helper.h"
 #include "test/cpp/util/test_credentials_provider.h"
 
-#ifdef GRPC_POSIX_SOCKET
-#include "src/core/lib/iomgr/ev_posix.h"
-#endif  // GRPC_POSIX_SOCKET
-
 #include <gtest/gtest.h>
 
 using grpc::testing::EchoRequest;
@@ -812,12 +809,11 @@ TEST_P(End2endTest, ReconnectChannel) {
   int poller_slowdown_factor = 1;
   // It needs 2 pollset_works to reconnect the channel with polling engine
   // "poll"
-#ifdef GRPC_POSIX_SOCKET
-  grpc_core::UniquePtr<char> poller = GPR_GLOBAL_CONFIG_GET(grpc_poll_strategy);
-  if (0 == strcmp(poller.get(), "poll")) {
+  char* s = gpr_getenv("GRPC_POLL_STRATEGY");
+  if (s != nullptr && 0 == strcmp(s, "poll")) {
     poller_slowdown_factor = 2;
   }
-#endif  // GRPC_POSIX_SOCKET
+  gpr_free(s);
   ResetStub();
   SendRpc(stub_.get(), 1, false);
   RestartServer(std::shared_ptr<AuthMetadataProcessor>());
diff --git a/test/cpp/end2end/service_config_end2end_test.cc b/test/cpp/end2end/service_config_end2end_test.cc
index 2d05fd42635..b3299232763 100644
--- a/test/cpp/end2end/service_config_end2end_test.cc
+++ b/test/cpp/end2end/service_config_end2end_test.cc
@@ -237,6 +237,14 @@ class ServiceConfigEnd2endTest : public ::testing::Test {
     return ::grpc::CreateCustomChannel("fake:///", creds_, args);
   }
 
+  std::shared_ptr<Channel> BuildChannelWithInvalidDefaultServiceConfig() {
+    ChannelArguments args;
+    args.SetServiceConfigJSON(InvalidDefaultServiceConfig());
+    args.SetPointer(GRPC_ARG_FAKE_RESOLVER_RESPONSE_GENERATOR,
+                    response_generator_.get());
+    return ::grpc::CreateCustomChannel("fake:///", creds_, args);
+  }
+
   bool SendRpc(
       const std::unique_ptr<grpc::testing::EchoTestService::Stub>& stub,
       EchoResponse* response = nullptr, int timeout_ms = 1000,
@@ -402,7 +410,7 @@ class ServiceConfigEnd2endTest : public ::testing::Test {
   }
 
   const char* InvalidDefaultServiceConfig() {
-    return "{\"version\": \"invalid_default\"}";
+    return "{\"version\": \"invalid_default\"";
   }
 
   const grpc::string server_host_;
@@ -549,6 +557,51 @@ TEST_F(ServiceConfigEnd2endTest,
   CheckRpcSendFailure(stub);
 }
 
+TEST_F(ServiceConfigEnd2endTest, InvalidDefaultServiceConfigTest) {
+  StartServers(1);
+  auto channel = BuildChannelWithInvalidDefaultServiceConfig();
+  auto stub = BuildStub(channel);
+  // An invalid default service config results in a lame channel which fails all
+  // RPCs
+  CheckRpcSendFailure(stub);
+}
+
+TEST_F(ServiceConfigEnd2endTest,
+       InvalidDefaultServiceConfigTestWithValidServiceConfig) {
+  StartServers(1);
+  auto channel = BuildChannelWithInvalidDefaultServiceConfig();
+  auto stub = BuildStub(channel);
+  CheckRpcSendFailure(stub);
+  // An invalid default service config results in a lame channel which fails all
+  // RPCs
+  SetNextResolutionValidServiceConfig(GetServersPorts());
+  CheckRpcSendFailure(stub);
+}
+
+TEST_F(ServiceConfigEnd2endTest,
+       InvalidDefaultServiceConfigTestWithInvalidServiceConfig) {
+  StartServers(1);
+  auto channel = BuildChannelWithInvalidDefaultServiceConfig();
+  auto stub = BuildStub(channel);
+  CheckRpcSendFailure(stub);
+  // An invalid default service config results in a lame channel which fails all
+  // RPCs
+  SetNextResolutionInvalidServiceConfig(GetServersPorts());
+  CheckRpcSendFailure(stub);
+}
+
+TEST_F(ServiceConfigEnd2endTest,
+       InvalidDefaultServiceConfigTestWithNoServiceConfig) {
+  StartServers(1);
+  auto channel = BuildChannelWithInvalidDefaultServiceConfig();
+  auto stub = BuildStub(channel);
+  CheckRpcSendFailure(stub);
+  // An invalid default service config results in a lame channel which fails all
+  // RPCs
+  SetNextResolutionNoServiceConfig(GetServersPorts());
+  CheckRpcSendFailure(stub);
+}
+
 }  // namespace
 }  // namespace testing
 }  // namespace grpc
diff --git a/test/cpp/microbenchmarks/BUILD b/test/cpp/microbenchmarks/BUILD
index 6e844a6dc62..d9424f24f16 100644
--- a/test/cpp/microbenchmarks/BUILD
+++ b/test/cpp/microbenchmarks/BUILD
@@ -39,85 +39,85 @@ grpc_cc_library(
     external_deps = [
         "benchmark",
     ],
+    tags = ["no_windows"],
     deps = [
         "//:grpc++_unsecure",
         "//src/proto/grpc/testing:echo_proto",
         "//test/core/util:grpc_test_util_unsecure",
         "//test/cpp/util:test_config",
     ],
-    tags = ["no_windows"],
 )
 
 grpc_cc_binary(
     name = "bm_closure",
     testonly = 1,
     srcs = ["bm_closure.cc"],
-    deps = [":helpers"],
     tags = ["no_windows"],
+    deps = [":helpers"],
 )
 
 grpc_cc_binary(
     name = "bm_alarm",
     testonly = 1,
     srcs = ["bm_alarm.cc"],
-    deps = [":helpers"],
     tags = ["no_windows"],
+    deps = [":helpers"],
 )
 
 grpc_cc_binary(
     name = "bm_arena",
     testonly = 1,
     srcs = ["bm_arena.cc"],
-    deps = [":helpers"],
     tags = ["no_windows"],
+    deps = [":helpers"],
 )
 
 grpc_cc_binary(
     name = "bm_byte_buffer",
     testonly = 1,
     srcs = ["bm_byte_buffer.cc"],
-    deps = [":helpers"],
     tags = ["no_windows"],
+    deps = [":helpers"],
 )
 
 grpc_cc_binary(
     name = "bm_channel",
     testonly = 1,
     srcs = ["bm_channel.cc"],
-    deps = [":helpers"],
     tags = ["no_windows"],
+    deps = [":helpers"],
 )
 
 grpc_cc_binary(
     name = "bm_call_create",
     testonly = 1,
     srcs = ["bm_call_create.cc"],
-    deps = [":helpers"],
     tags = ["no_windows"],
+    deps = [":helpers"],
 )
 
 grpc_cc_binary(
     name = "bm_cq",
     testonly = 1,
     srcs = ["bm_cq.cc"],
-    deps = [":helpers"],
     tags = ["no_windows"],
+    deps = [":helpers"],
 )
 
 grpc_cc_binary(
     name = "bm_cq_multiple_threads",
     testonly = 1,
     srcs = ["bm_cq_multiple_threads.cc"],
-    deps = [":helpers"],
     tags = ["no_windows"],
+    deps = [":helpers"],
 )
 
 grpc_cc_binary(
     name = "bm_error",
     testonly = 1,
     srcs = ["bm_error.cc"],
-    deps = [":helpers"],
     tags = ["no_windows"],
+    deps = [":helpers"],
 )
 
 grpc_cc_library(
@@ -126,8 +126,8 @@ grpc_cc_library(
     hdrs = [
         "fullstack_streaming_ping_pong.h",
     ],
-    deps = [":helpers"],
     tags = ["no_windows"],
+    deps = [":helpers"],
 )
 
 grpc_cc_binary(
@@ -136,8 +136,8 @@ grpc_cc_binary(
     srcs = [
         "bm_fullstack_streaming_ping_pong.cc",
     ],
-    deps = [":fullstack_streaming_ping_pong_h"],
     tags = ["no_windows"],
+    deps = [":fullstack_streaming_ping_pong_h"],
 )
 
 grpc_cc_library(
@@ -155,16 +155,16 @@ grpc_cc_binary(
     srcs = [
         "bm_fullstack_streaming_pump.cc",
     ],
-    deps = [":fullstack_streaming_pump_h"],
     tags = ["no_windows"],
+    deps = [":fullstack_streaming_pump_h"],
 )
 
 grpc_cc_binary(
     name = "bm_fullstack_trickle",
     testonly = 1,
     srcs = ["bm_fullstack_trickle.cc"],
-    deps = [":helpers"],
     tags = ["no_windows"],
+    deps = [":helpers"],
 )
 
 grpc_cc_library(
@@ -182,24 +182,24 @@ grpc_cc_binary(
     srcs = [
         "bm_fullstack_unary_ping_pong.cc",
     ],
-    deps = [":fullstack_unary_ping_pong_h"],
     tags = ["no_windows"],
+    deps = [":fullstack_unary_ping_pong_h"],
 )
 
 grpc_cc_binary(
     name = "bm_metadata",
     testonly = 1,
     srcs = ["bm_metadata.cc"],
-    deps = [":helpers"],
     tags = ["no_windows"],
+    deps = [":helpers"],
 )
 
 grpc_cc_binary(
     name = "bm_chttp2_hpack",
     testonly = 1,
     srcs = ["bm_chttp2_hpack.cc"],
-    deps = [":helpers"],
     tags = ["no_windows"],
+    deps = [":helpers"],
 )
 
 grpc_cc_binary(
@@ -218,6 +218,65 @@ grpc_cc_binary(
     name = "bm_timer",
     testonly = 1,
     srcs = ["bm_timer.cc"],
-    deps = [":helpers"],
     tags = ["no_windows"],
+    deps = [":helpers"],
+)
+
+grpc_cc_library(
+    name = "bm_callback_test_service_impl",
+    testonly = 1,
+    srcs = ["callback_test_service.cc"],
+    hdrs = ["callback_test_service.h"],
+    external_deps = [
+        "benchmark",
+    ],
+    deps = [
+        ":helpers",
+        "//src/proto/grpc/testing:echo_proto",
+        "//test/cpp/util:test_util",
+    ],
+)
+
+grpc_cc_library(
+    name = "callback_unary_ping_pong_h",
+    testonly = 1,
+    hdrs = [
+        "callback_unary_ping_pong.h",
+    ],
+    deps = [
+        ":bm_callback_test_service_impl",
+        ":helpers",
+    ],
+)
+
+grpc_cc_binary(
+    name = "bm_callback_unary_ping_pong",
+    testonly = 1,
+    srcs = [
+        "bm_callback_unary_ping_pong.cc",
+    ],
+    tags = ["no_windows"],
+    deps = [":callback_unary_ping_pong_h"],
+)
+
+grpc_cc_library(
+    name = "callback_streaming_ping_pong_h",
+    testonly = 1,
+    hdrs = [
+        "callback_streaming_ping_pong.h",
+    ],
+    deps = [
+        ":bm_callback_test_service_impl",
+        ":helpers",
+    ],
+)
+
+grpc_cc_binary(
+    name = "bm_callback_streaming_ping_pong",
+    testonly = 1,
+    srcs = [
+        "bm_callback_streaming_ping_pong.cc",
+    ],
+    tags = ["no_windows"],
+    deps = [":callback_streaming_ping_pong_h"],
 )
diff --git a/test/cpp/microbenchmarks/bm_callback_streaming_ping_pong.cc b/test/cpp/microbenchmarks/bm_callback_streaming_ping_pong.cc
new file mode 100644
index 00000000000..cde3eb2a241
--- /dev/null
+++ b/test/cpp/microbenchmarks/bm_callback_streaming_ping_pong.cc
@@ -0,0 +1,136 @@
+/*
+ *
+ * Copyright 2019 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include "test/cpp/microbenchmarks/callback_streaming_ping_pong.h"
+#include "test/cpp/util/test_config.h"
+
+namespace grpc {
+namespace testing {
+
+/*******************************************************************************
+ * CONFIGURATIONS
+ */
+
+// Replace "benchmark::internal::Benchmark" with "::testing::Benchmark" to use
+// internal microbenchmarking tooling
+static void StreamingPingPongMsgSizeArgs(benchmark::internal::Benchmark* b) {
+  // base case: 0 byte ping-pong msgs
+  b->Args({0, 1});
+  b->Args({0, 2});
+
+  for (int msg_size = 1; msg_size <= 128 * 1024 * 1024; msg_size *= 8) {
+    b->Args({msg_size, 1});
+    b->Args({msg_size, 2});
+  }
+}
+
+// Replace "benchmark::internal::Benchmark" with "::testing::Benchmark" to use
+// internal microbenchmarking tooling
+static void StreamingPingPongMsgsNumberArgs(benchmark::internal::Benchmark* b) {
+  for (int msg_number = 1; msg_number <= 256 * 1024; msg_number *= 8) {
+    b->Args({0, msg_number});
+    b->Args({1024, msg_number});
+  }
+}
+
+// Streaming with different message size
+BENCHMARK_TEMPLATE(BM_CallbackBidiStreaming, InProcess, NoOpMutator,
+                   NoOpMutator)
+    ->Apply(StreamingPingPongMsgSizeArgs);
+BENCHMARK_TEMPLATE(BM_CallbackBidiStreaming, MinInProcess, NoOpMutator,
+                   NoOpMutator)
+    ->Apply(StreamingPingPongMsgSizeArgs);
+
+// Streaming with different message number
+BENCHMARK_TEMPLATE(BM_CallbackBidiStreaming, InProcess, NoOpMutator,
+                   NoOpMutator)
+    ->Apply(StreamingPingPongMsgsNumberArgs);
+BENCHMARK_TEMPLATE(BM_CallbackBidiStreaming, MinInProcess, NoOpMutator,
+                   NoOpMutator)
+    ->Apply(StreamingPingPongMsgsNumberArgs);
+
+// Client context with different metadata
+BENCHMARK_TEMPLATE(BM_CallbackBidiStreaming, InProcess,
+                   Client_AddMetadata<RandomBinaryMetadata<10>, 1>, NoOpMutator)
+    ->Args({0, 1});
+BENCHMARK_TEMPLATE(BM_CallbackBidiStreaming, InProcess,
+                   Client_AddMetadata<RandomBinaryMetadata<31>, 1>, NoOpMutator)
+    ->Args({0, 1});
+BENCHMARK_TEMPLATE(BM_CallbackBidiStreaming, InProcess,
+                   Client_AddMetadata<RandomBinaryMetadata<100>, 1>,
+                   NoOpMutator)
+    ->Args({0, 1});
+BENCHMARK_TEMPLATE(BM_CallbackBidiStreaming, InProcess,
+                   Client_AddMetadata<RandomBinaryMetadata<10>, 2>, NoOpMutator)
+    ->Args({0, 1});
+BENCHMARK_TEMPLATE(BM_CallbackBidiStreaming, InProcess,
+                   Client_AddMetadata<RandomBinaryMetadata<31>, 2>, NoOpMutator)
+    ->Args({0, 1});
+BENCHMARK_TEMPLATE(BM_CallbackBidiStreaming, InProcess,
+                   Client_AddMetadata<RandomBinaryMetadata<100>, 2>,
+                   NoOpMutator)
+    ->Args({0, 1});
+BENCHMARK_TEMPLATE(BM_CallbackBidiStreaming, InProcess,
+                   Client_AddMetadata<RandomAsciiMetadata<10>, 1>, NoOpMutator)
+    ->Args({0, 1});
+BENCHMARK_TEMPLATE(BM_CallbackBidiStreaming, InProcess,
+                   Client_AddMetadata<RandomAsciiMetadata<31>, 1>, NoOpMutator)
+    ->Args({0, 1});
+BENCHMARK_TEMPLATE(BM_CallbackBidiStreaming, InProcess,
+                   Client_AddMetadata<RandomAsciiMetadata<100>, 1>, NoOpMutator)
+    ->Args({0, 1});
+
+// Server context with different metadata
+BENCHMARK_TEMPLATE(BM_CallbackBidiStreaming, InProcess, NoOpMutator,
+                   Server_AddInitialMetadata<RandomBinaryMetadata<10>, 1>)
+    ->Args({0, 1});
+BENCHMARK_TEMPLATE(BM_CallbackBidiStreaming, InProcess, NoOpMutator,
+                   Server_AddInitialMetadata<RandomBinaryMetadata<31>, 1>)
+    ->Args({0, 1});
+BENCHMARK_TEMPLATE(BM_CallbackBidiStreaming, InProcess, NoOpMutator,
+                   Server_AddInitialMetadata<RandomBinaryMetadata<100>, 1>)
+    ->Args({0, 1});
+BENCHMARK_TEMPLATE(BM_CallbackBidiStreaming, InProcess, NoOpMutator,
+                   Server_AddInitialMetadata<RandomAsciiMetadata<10>, 1>)
+    ->Args({0, 1});
+BENCHMARK_TEMPLATE(BM_CallbackBidiStreaming, InProcess, NoOpMutator,
+                   Server_AddInitialMetadata<RandomAsciiMetadata<31>, 1>)
+    ->Args({0, 1});
+BENCHMARK_TEMPLATE(BM_CallbackBidiStreaming, InProcess, NoOpMutator,
+                   Server_AddInitialMetadata<RandomAsciiMetadata<100>, 1>)
+    ->Args({0, 1});
+BENCHMARK_TEMPLATE(BM_CallbackBidiStreaming, InProcess, NoOpMutator,
+                   Server_AddInitialMetadata<RandomAsciiMetadata<10>, 100>)
+    ->Args({0, 1});
+
+}  // namespace testing
+}  // namespace grpc
+
+// Some distros have RunSpecifiedBenchmarks under the benchmark namespace,
+// and others do not. This allows us to support both modes.
+namespace benchmark {
+void RunTheBenchmarksNamespaced() { RunSpecifiedBenchmarks(); }
+}  // namespace benchmark
+
+int main(int argc, char** argv) {
+  LibraryInitializer libInit;
+  ::benchmark::Initialize(&argc, argv);
+  ::grpc::testing::InitTest(&argc, &argv, false);
+  benchmark::RunTheBenchmarksNamespaced();
+  return 0;
+}
diff --git a/test/cpp/microbenchmarks/bm_callback_unary_ping_pong.cc b/test/cpp/microbenchmarks/bm_callback_unary_ping_pong.cc
new file mode 100644
index 00000000000..4ee77525bc6
--- /dev/null
+++ b/test/cpp/microbenchmarks/bm_callback_unary_ping_pong.cc
@@ -0,0 +1,118 @@
+/*
+ *
+ * Copyright 2019 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include "test/cpp/microbenchmarks/callback_unary_ping_pong.h"
+#include "test/cpp/util/test_config.h"
+
+namespace grpc {
+namespace testing {
+
+/*******************************************************************************
+ * CONFIGURATIONS
+ */
+
+// Replace "benchmark::internal::Benchmark" with "::testing::Benchmark" to use
+// internal microbenchmarking tooling
+static void SweepSizesArgs(benchmark::internal::Benchmark* b) {
+  b->Args({0, 0});
+  for (int i = 1; i <= 128 * 1024 * 1024; i *= 8) {
+    // First argument is the message size of request
+    // Second argument is the message size of response
+    b->Args({i, 0});
+    b->Args({0, i});
+    b->Args({i, i});
+  }
+}
+
+// Unary ping pong with different message size of request and response
+BENCHMARK_TEMPLATE(BM_CallbackUnaryPingPong, InProcess, NoOpMutator,
+                   NoOpMutator)
+    ->Apply(SweepSizesArgs);
+BENCHMARK_TEMPLATE(BM_CallbackUnaryPingPong, MinInProcess, NoOpMutator,
+                   NoOpMutator)
+    ->Apply(SweepSizesArgs);
+
+// Client context with different metadata
+BENCHMARK_TEMPLATE(BM_CallbackUnaryPingPong, InProcess,
+                   Client_AddMetadata<RandomBinaryMetadata<10>, 1>, NoOpMutator)
+    ->Args({0, 0});
+BENCHMARK_TEMPLATE(BM_CallbackUnaryPingPong, InProcess,
+                   Client_AddMetadata<RandomBinaryMetadata<31>, 1>, NoOpMutator)
+    ->Args({0, 0});
+BENCHMARK_TEMPLATE(BM_CallbackUnaryPingPong, InProcess,
+                   Client_AddMetadata<RandomBinaryMetadata<100>, 1>,
+                   NoOpMutator)
+    ->Args({0, 0});
+BENCHMARK_TEMPLATE(BM_CallbackUnaryPingPong, InProcess,
+                   Client_AddMetadata<RandomBinaryMetadata<10>, 2>, NoOpMutator)
+    ->Args({0, 0});
+BENCHMARK_TEMPLATE(BM_CallbackUnaryPingPong, InProcess,
+                   Client_AddMetadata<RandomBinaryMetadata<31>, 2>, NoOpMutator)
+    ->Args({0, 0});
+BENCHMARK_TEMPLATE(BM_CallbackUnaryPingPong, InProcess,
+                   Client_AddMetadata<RandomBinaryMetadata<100>, 2>,
+                   NoOpMutator)
+    ->Args({0, 0});
+BENCHMARK_TEMPLATE(BM_CallbackUnaryPingPong, InProcess,
+                   Client_AddMetadata<RandomAsciiMetadata<10>, 1>, NoOpMutator)
+    ->Args({0, 0});
+BENCHMARK_TEMPLATE(BM_CallbackUnaryPingPong, InProcess,
+                   Client_AddMetadata<RandomAsciiMetadata<31>, 1>, NoOpMutator)
+    ->Args({0, 0});
+BENCHMARK_TEMPLATE(BM_CallbackUnaryPingPong, InProcess,
+                   Client_AddMetadata<RandomAsciiMetadata<100>, 1>, NoOpMutator)
+    ->Args({0, 0});
+
+// Server context with different metadata
+BENCHMARK_TEMPLATE(BM_CallbackUnaryPingPong, InProcess, NoOpMutator,
+                   Server_AddInitialMetadata<RandomBinaryMetadata<10>, 1>)
+    ->Args({0, 0});
+BENCHMARK_TEMPLATE(BM_CallbackUnaryPingPong, InProcess, NoOpMutator,
+                   Server_AddInitialMetadata<RandomBinaryMetadata<31>, 1>)
+    ->Args({0, 0});
+BENCHMARK_TEMPLATE(BM_CallbackUnaryPingPong, InProcess, NoOpMutator,
+                   Server_AddInitialMetadata<RandomBinaryMetadata<100>, 1>)
+    ->Args({0, 0});
+BENCHMARK_TEMPLATE(BM_CallbackUnaryPingPong, InProcess, NoOpMutator,
+                   Server_AddInitialMetadata<RandomAsciiMetadata<10>, 1>)
+    ->Args({0, 0});
+BENCHMARK_TEMPLATE(BM_CallbackUnaryPingPong, InProcess, NoOpMutator,
+                   Server_AddInitialMetadata<RandomAsciiMetadata<31>, 1>)
+    ->Args({0, 0});
+BENCHMARK_TEMPLATE(BM_CallbackUnaryPingPong, InProcess, NoOpMutator,
+                   Server_AddInitialMetadata<RandomAsciiMetadata<100>, 1>)
+    ->Args({0, 0});
+BENCHMARK_TEMPLATE(BM_CallbackUnaryPingPong, InProcess, NoOpMutator,
+                   Server_AddInitialMetadata<RandomAsciiMetadata<10>, 100>)
+    ->Args({0, 0});
+}  // namespace testing
+}  // namespace grpc
+
+// Some distros have RunSpecifiedBenchmarks under the benchmark namespace,
+// and others do not. This allows us to support both modes.
+namespace benchmark {
+void RunTheBenchmarksNamespaced() { RunSpecifiedBenchmarks(); }
+}  // namespace benchmark
+
+int main(int argc, char** argv) {
+  LibraryInitializer libInit;
+  ::benchmark::Initialize(&argc, argv);
+  ::grpc::testing::InitTest(&argc, &argv, false);
+  benchmark::RunTheBenchmarksNamespaced();
+  return 0;
+}
diff --git a/test/cpp/microbenchmarks/bm_cq.cc b/test/cpp/microbenchmarks/bm_cq.cc
index 263314deb93..50eb9454fbe 100644
--- a/test/cpp/microbenchmarks/bm_cq.cc
+++ b/test/cpp/microbenchmarks/bm_cq.cc
@@ -144,6 +144,66 @@ static void BM_EmptyCore(benchmark::State& state) {
 }
 BENCHMARK(BM_EmptyCore);
 
+// Helper for tests to shutdown correctly and tersely
+static void shutdown_and_destroy(grpc_completion_queue* cc) {
+  grpc_completion_queue_shutdown(cc);
+  grpc_completion_queue_destroy(cc);
+}
+
+// Tag completion queue iterate times
+class TagCallback : public grpc_experimental_completion_queue_functor {
+ public:
+  explicit TagCallback(int* iter) : iter_(iter) {
+    functor_run = &TagCallback::Run;
+  }
+  ~TagCallback() {}
+  static void Run(grpc_experimental_completion_queue_functor* cb, int ok) {
+    GPR_ASSERT(static_cast<bool>(ok));
+    *static_cast<TagCallback*>(cb)->iter_ += 1;
+  };
+
+ private:
+  int* iter_;
+};
+
+// Check if completion queue is shut down
+class ShutdownCallback : public grpc_experimental_completion_queue_functor {
+ public:
+  explicit ShutdownCallback(bool* done) : done_(done) {
+    functor_run = &ShutdownCallback::Run;
+  }
+  ~ShutdownCallback() {}
+  static void Run(grpc_experimental_completion_queue_functor* cb, int ok) {
+    *static_cast<ShutdownCallback*>(cb)->done_ = static_cast<bool>(ok);
+  }
+
+ private:
+  bool* done_;
+};
+
+static void BM_Callback_CQ_Pass1Core(benchmark::State& state) {
+  TrackCounters track_counters;
+  int iteration = 0;
+  TagCallback tag_cb(&iteration);
+  bool got_shutdown = false;
+  ShutdownCallback shutdown_cb(&got_shutdown);
+  grpc_completion_queue* cc =
+      grpc_completion_queue_create_for_callback(&shutdown_cb, nullptr);
+  while (state.KeepRunning()) {
+    grpc_core::ApplicationCallbackExecCtx callback_exec_ctx;
+    grpc_core::ExecCtx exec_ctx;
+    grpc_cq_completion completion;
+    GPR_ASSERT(grpc_cq_begin_op(cc, &tag_cb));
+    grpc_cq_end_op(cc, &tag_cb, GRPC_ERROR_NONE, DoneWithCompletionOnStack,
+                   nullptr, &completion);
+  }
+  shutdown_and_destroy(cc);
+  GPR_ASSERT(got_shutdown);
+  GPR_ASSERT(iteration == static_cast<int>(state.iterations()));
+  track_counters.Finish(state);
+}
+BENCHMARK(BM_Callback_CQ_Pass1Core);
+
 }  // namespace testing
 }  // namespace grpc
 
diff --git a/test/cpp/microbenchmarks/callback_streaming_ping_pong.h b/test/cpp/microbenchmarks/callback_streaming_ping_pong.h
new file mode 100644
index 00000000000..9fb86bd8299
--- /dev/null
+++ b/test/cpp/microbenchmarks/callback_streaming_ping_pong.h
@@ -0,0 +1,150 @@
+/*
+ *
+ * Copyright 2019 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef TEST_CPP_MICROBENCHMARKS_CALLBACK_STREAMING_PING_PONG_H
+#define TEST_CPP_MICROBENCHMARKS_CALLBACK_STREAMING_PING_PONG_H
+
+#include <benchmark/benchmark.h>
+#include <sstream>
+#include "src/core/lib/profiling/timers.h"
+#include "src/proto/grpc/testing/echo.grpc.pb.h"
+#include "test/cpp/microbenchmarks/callback_test_service.h"
+#include "test/cpp/microbenchmarks/fullstack_context_mutators.h"
+#include "test/cpp/microbenchmarks/fullstack_fixtures.h"
+
+namespace grpc {
+namespace testing {
+
+/*******************************************************************************
+ * BENCHMARKING KERNELS
+ */
+
+class BidiClient
+    : public grpc::experimental::ClientBidiReactor<EchoRequest, EchoResponse> {
+ public:
+  BidiClient(benchmark::State* state, EchoTestService::Stub* stub,
+             ClientContext* cli_ctx, EchoRequest* request,
+             EchoResponse* response)
+      : state_{state},
+        stub_{stub},
+        cli_ctx_{cli_ctx},
+        request_{request},
+        response_{response} {
+    msgs_size_ = state->range(0);
+    msgs_to_send_ = state->range(1);
+    StartNewRpc();
+  }
+
+  void OnReadDone(bool ok) override {
+    if (!ok) {
+      gpr_log(GPR_ERROR, "Client read failed");
+      return;
+    }
+    MaybeWrite();
+  }
+
+  void OnWriteDone(bool ok) override {
+    if (!ok) {
+      gpr_log(GPR_ERROR, "Client write failed");
+      return;
+    }
+    writes_complete_++;
+    StartRead(response_);
+  }
+
+  void OnDone(const Status& s) override {
+    GPR_ASSERT(s.ok());
+    GPR_ASSERT(writes_complete_ == msgs_to_send_);
+    if (state_->KeepRunning()) {
+      writes_complete_ = 0;
+      StartNewRpc();
+    } else {
+      std::unique_lock<std::mutex> l(mu);
+      done = true;
+      cv.notify_one();
+    }
+  }
+
+  void StartNewRpc() {
+    cli_ctx_->~ClientContext();
+    new (cli_ctx_) ClientContext();
+    cli_ctx_->AddMetadata(kServerMessageSize, grpc::to_string(msgs_size_));
+    stub_->experimental_async()->BidiStream(cli_ctx_, this);
+    MaybeWrite();
+    StartCall();
+  }
+
+  void Await() {
+    std::unique_lock<std::mutex> l(mu);
+    while (!done) {
+      cv.wait(l);
+    }
+  }
+
+ private:
+  void MaybeWrite() {
+    if (writes_complete_ < msgs_to_send_) {
+      StartWrite(request_);
+    } else {
+      StartWritesDone();
+    }
+  }
+
+  benchmark::State* state_;
+  EchoTestService::Stub* stub_;
+  ClientContext* cli_ctx_;
+  EchoRequest* request_;
+  EchoResponse* response_;
+  int writes_complete_{0};
+  int msgs_to_send_;
+  int msgs_size_;
+  std::mutex mu;
+  std::condition_variable cv;
+  bool done;
+};
+
+template <class Fixture, class ClientContextMutator, class ServerContextMutator>
+static void BM_CallbackBidiStreaming(benchmark::State& state) {
+  int message_size = state.range(0);
+  int max_ping_pongs = state.range(1);
+  CallbackStreamingTestService service;
+  std::unique_ptr<Fixture> fixture(new Fixture(&service));
+  std::unique_ptr<EchoTestService::Stub> stub_(
+      EchoTestService::NewStub(fixture->channel()));
+  EchoRequest request;
+  EchoResponse response;
+  ClientContext cli_ctx;
+  if (message_size > 0) {
+    request.set_message(std::string(message_size, 'a'));
+  } else {
+    request.set_message("");
+  }
+  if (state.KeepRunning()) {
+    GPR_TIMER_SCOPE("BenchmarkCycle", 0);
+    BidiClient test{&state, stub_.get(), &cli_ctx, &request, &response};
+    test.Await();
+  }
+  fixture->Finish(state);
+  fixture.reset();
+  state.SetBytesProcessed(2 * message_size * max_ping_pongs *
+                          state.iterations());
+}
+
+}  // namespace testing
+}  // namespace grpc
+#endif  // TEST_CPP_MICROBENCHMARKS_CALLBACK_STREAMING_PING_PONG_H
diff --git a/test/cpp/microbenchmarks/callback_test_service.cc b/test/cpp/microbenchmarks/callback_test_service.cc
new file mode 100644
index 00000000000..321a5b39184
--- /dev/null
+++ b/test/cpp/microbenchmarks/callback_test_service.cc
@@ -0,0 +1,112 @@
+/*
+ *
+ * Copyright 2019 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include "test/cpp/microbenchmarks/callback_test_service.h"
+
+namespace grpc {
+namespace testing {
+namespace {
+
+grpc::string ToString(const grpc::string_ref& r) {
+  return grpc::string(r.data(), r.size());
+}
+
+int GetIntValueFromMetadataHelper(
+    const char* key,
+    const std::multimap<grpc::string_ref, grpc::string_ref>& metadata,
+    int default_value) {
+  if (metadata.find(key) != metadata.end()) {
+    std::istringstream iss(ToString(metadata.find(key)->second));
+    iss >> default_value;
+  }
+
+  return default_value;
+}
+
+int GetIntValueFromMetadata(
+    const char* key,
+    const std::multimap<grpc::string_ref, grpc::string_ref>& metadata,
+    int default_value) {
+  return GetIntValueFromMetadataHelper(key, metadata, default_value);
+}
+}  // namespace
+
+void CallbackStreamingTestService::Echo(
+    ServerContext* context, const EchoRequest* request, EchoResponse* response,
+    experimental::ServerCallbackRpcController* controller) {
+  int response_msgs_size = GetIntValueFromMetadata(
+      kServerMessageSize, context->client_metadata(), 0);
+  if (response_msgs_size > 0) {
+    response->set_message(std::string(response_msgs_size, 'a'));
+  } else {
+    response->set_message("");
+  }
+  controller->Finish(Status::OK);
+}
+
+experimental::ServerBidiReactor<EchoRequest, EchoResponse>*
+CallbackStreamingTestService::BidiStream() {
+  class Reactor
+      : public experimental::ServerBidiReactor<EchoRequest, EchoResponse> {
+   public:
+    Reactor() {}
+    void OnStarted(ServerContext* context) override {
+      ctx_ = context;
+      message_size_ = GetIntValueFromMetadata(kServerMessageSize,
+                                              context->client_metadata(), 0);
+      StartRead(&request_);
+    }
+    void OnDone() override {
+      GPR_ASSERT(finished_);
+      delete this;
+    }
+    void OnCancel() override {}
+    void OnReadDone(bool ok) override {
+      if (!ok) {
+        // Stream is over
+        Finish(::grpc::Status::OK);
+        finished_ = true;
+        return;
+      }
+      if (message_size_ > 0) {
+        response_.set_message(std::string(message_size_, 'a'));
+      } else {
+        response_.set_message("");
+      }
+      StartWrite(&response_);
+    }
+    void OnWriteDone(bool ok) override {
+      if (!ok) {
+        gpr_log(GPR_ERROR, "Server write failed");
+        return;
+      }
+      StartRead(&request_);
+    }
+
+   private:
+    ServerContext* ctx_;
+    EchoRequest request_;
+    EchoResponse response_;
+    int message_size_;
+    bool finished_{false};
+  };
+
+  return new Reactor;
+}
+}  // namespace testing
+}  // namespace grpc
diff --git a/test/cpp/microbenchmarks/callback_test_service.h b/test/cpp/microbenchmarks/callback_test_service.h
new file mode 100644
index 00000000000..97188595382
--- /dev/null
+++ b/test/cpp/microbenchmarks/callback_test_service.h
@@ -0,0 +1,48 @@
+/*
+ *
+ * Copyright 2019 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef TEST_CPP_MICROBENCHMARKS_CALLBACK_TEST_SERVICE_H
+#define TEST_CPP_MICROBENCHMARKS_CALLBACK_TEST_SERVICE_H
+
+#include <benchmark/benchmark.h>
+#include <condition_variable>
+#include <memory>
+#include <mutex>
+#include <sstream>
+#include "src/proto/grpc/testing/echo.grpc.pb.h"
+#include "test/cpp/util/string_ref_helper.h"
+
+namespace grpc {
+namespace testing {
+
+const char* const kServerMessageSize = "server_message_size";
+
+class CallbackStreamingTestService
+    : public EchoTestService::ExperimentalCallbackService {
+ public:
+  CallbackStreamingTestService() {}
+  void Echo(ServerContext* context, const EchoRequest* request,
+            EchoResponse* response,
+            experimental::ServerCallbackRpcController* controller) override;
+
+  experimental::ServerBidiReactor<EchoRequest, EchoResponse>* BidiStream()
+      override;
+};
+}  // namespace testing
+}  // namespace grpc
+#endif  // TEST_CPP_MICROBENCHMARKS_CALLBACK_TEST_SERVICE_H
diff --git a/test/cpp/microbenchmarks/callback_unary_ping_pong.h b/test/cpp/microbenchmarks/callback_unary_ping_pong.h
new file mode 100644
index 00000000000..359b91eb6fe
--- /dev/null
+++ b/test/cpp/microbenchmarks/callback_unary_ping_pong.h
@@ -0,0 +1,101 @@
+/*
+ *
+ * Copyright 2019 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+/* Benchmark gRPC end2end in various configurations */
+
+#ifndef TEST_CPP_MICROBENCHMARKS_CALLBACK_UNARY_PING_PONG_H
+#define TEST_CPP_MICROBENCHMARKS_CALLBACK_UNARY_PING_PONG_H
+
+#include <benchmark/benchmark.h>
+#include <sstream>
+#include "src/core/lib/profiling/timers.h"
+#include "src/proto/grpc/testing/echo.grpc.pb.h"
+#include "test/cpp/microbenchmarks/callback_test_service.h"
+#include "test/cpp/microbenchmarks/fullstack_context_mutators.h"
+#include "test/cpp/microbenchmarks/fullstack_fixtures.h"
+
+namespace grpc {
+namespace testing {
+
+/*******************************************************************************
+ * BENCHMARKING KERNELS
+ */
+
+void SendCallbackUnaryPingPong(benchmark::State* state, ClientContext* cli_ctx,
+                               EchoRequest* request, EchoResponse* response,
+                               EchoTestService::Stub* stub_, bool* done,
+                               std::mutex* mu, std::condition_variable* cv) {
+  int response_msgs_size = state->range(1);
+  cli_ctx->AddMetadata(kServerMessageSize, grpc::to_string(response_msgs_size));
+  stub_->experimental_async()->Echo(
+      cli_ctx, request, response,
+      [state, cli_ctx, request, response, stub_, done, mu, cv](Status s) {
+        GPR_ASSERT(s.ok());
+        if (state->KeepRunning()) {
+          cli_ctx->~ClientContext();
+          new (cli_ctx) ClientContext();
+          SendCallbackUnaryPingPong(state, cli_ctx, request, response, stub_,
+                                    done, mu, cv);
+        } else {
+          std::lock_guard<std::mutex> l(*mu);
+          *done = true;
+          cv->notify_one();
+        }
+      });
+};
+
+template <class Fixture, class ClientContextMutator, class ServerContextMutator>
+static void BM_CallbackUnaryPingPong(benchmark::State& state) {
+  int request_msgs_size = state.range(0);
+  int response_msgs_size = state.range(1);
+  CallbackStreamingTestService service;
+  std::unique_ptr<Fixture> fixture(new Fixture(&service));
+  std::unique_ptr<EchoTestService::Stub> stub_(
+      EchoTestService::NewStub(fixture->channel()));
+  EchoRequest request;
+  EchoResponse response;
+  ClientContext cli_ctx;
+
+  if (request_msgs_size > 0) {
+    request.set_message(std::string(request_msgs_size, 'a'));
+  } else {
+    request.set_message("");
+  }
+
+  std::mutex mu;
+  std::condition_variable cv;
+  bool done = false;
+  if (state.KeepRunning()) {
+    GPR_TIMER_SCOPE("BenchmarkCycle", 0);
+    SendCallbackUnaryPingPong(&state, &cli_ctx, &request, &response,
+                              stub_.get(), &done, &mu, &cv);
+  }
+  std::unique_lock<std::mutex> l(mu);
+  while (!done) {
+    cv.wait(l);
+  }
+  fixture->Finish(state);
+  fixture.reset();
+  state.SetBytesProcessed(request_msgs_size * state.iterations() +
+                          response_msgs_size * state.iterations());
+}
+
+}  // namespace testing
+}  // namespace grpc
+
+#endif  // TEST_CPP_MICROBENCHMARKS_FULLSTACK_UNARY_PING_PONG_H
diff --git a/test/cpp/naming/address_sorting_test.cc b/test/cpp/naming/address_sorting_test.cc
index affc75bc634..bd685632c33 100644
--- a/test/cpp/naming/address_sorting_test.cc
+++ b/test/cpp/naming/address_sorting_test.cc
@@ -36,10 +36,10 @@
 #include "src/core/ext/filters/client_channel/client_channel.h"
 #include "src/core/ext/filters/client_channel/resolver.h"
 #include "src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.h"
-#include "src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.h"
 #include "src/core/ext/filters/client_channel/resolver_registry.h"
 #include "src/core/ext/filters/client_channel/server_address.h"
 #include "src/core/lib/channel/channel_args.h"
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/host_port.h"
 #include "src/core/lib/gpr/string.h"
 #include "src/core/lib/iomgr/combiner.h"
@@ -829,13 +829,13 @@ TEST_F(AddressSortingTest, TestSorterKnowsIpv6LoopbackIsAvailable) {
 }  // namespace
 
 int main(int argc, char** argv) {
-  grpc_core::UniquePtr<char> resolver =
-      GPR_GLOBAL_CONFIG_GET(grpc_dns_resolver);
-  if (strlen(resolver.get()) == 0) {
-    GPR_GLOBAL_CONFIG_SET(grpc_dns_resolver, "ares");
-  } else if (strcmp("ares", resolver.get())) {
-    gpr_log(GPR_INFO, "GRPC_DNS_RESOLVER != ares: %s.", resolver.get());
+  char* resolver = gpr_getenv("GRPC_DNS_RESOLVER");
+  if (resolver == nullptr || strlen(resolver) == 0) {
+    gpr_setenv("GRPC_DNS_RESOLVER", "ares");
+  } else if (strcmp("ares", resolver)) {
+    gpr_log(GPR_INFO, "GRPC_DNS_RESOLVER != ares: %s.", resolver);
   }
+  gpr_free(resolver);
   grpc::testing::TestEnvironment env(argc, argv);
   ::testing::InitGoogleTest(&argc, argv);
   auto result = RUN_ALL_TESTS();
diff --git a/test/cpp/naming/cancel_ares_query_test.cc b/test/cpp/naming/cancel_ares_query_test.cc
index 667011ae291..674e72fdc52 100644
--- a/test/cpp/naming/cancel_ares_query_test.cc
+++ b/test/cpp/naming/cancel_ares_query_test.cc
@@ -29,10 +29,10 @@
 #include <grpc/support/time.h>
 #include "include/grpc/support/string_util.h"
 #include "src/core/ext/filters/client_channel/resolver.h"
-#include "src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.h"
 #include "src/core/ext/filters/client_channel/resolver_registry.h"
 #include "src/core/lib/channel/channel_args.h"
 #include "src/core/lib/debug/stats.h"
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/host_port.h"
 #include "src/core/lib/gpr/string.h"
 #include "src/core/lib/gprpp/orphanable.h"
@@ -374,7 +374,7 @@ TEST(
 int main(int argc, char** argv) {
   grpc::testing::TestEnvironment env(argc, argv);
   ::testing::InitGoogleTest(&argc, argv);
-  GPR_GLOBAL_CONFIG_SET(grpc_dns_resolver, "ares");
+  gpr_setenv("GRPC_DNS_RESOLVER", "ares");
   // Sanity check the time that it takes to run the test
   // including the teardown time (the teardown
   // part of the test involves cancelling the DNS query,
diff --git a/test/cpp/naming/resolver_component_test.cc b/test/cpp/naming/resolver_component_test.cc
index 6cea8143907..93a92f68a6d 100644
--- a/test/cpp/naming/resolver_component_test.cc
+++ b/test/cpp/naming/resolver_component_test.cc
@@ -46,6 +46,7 @@
 #include "src/core/ext/filters/client_channel/resolver_registry.h"
 #include "src/core/ext/filters/client_channel/server_address.h"
 #include "src/core/lib/channel/channel_args.h"
+#include "src/core/lib/gpr/env.h"
 #include "src/core/lib/gpr/host_port.h"
 #include "src/core/lib/gpr/string.h"
 #include "src/core/lib/gprpp/orphanable.h"
diff --git a/tools/bazel.sh b/tools/bazel.sh
new file mode 100755
index 00000000000..37fd2a242bf
--- /dev/null
+++ b/tools/bazel.sh
@@ -0,0 +1,53 @@
+#!/bin/bash
+# Copyright 2019 The gRPC Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+# Keeping up with Bazel's breaking changes is currently difficult.
+# This script wraps calling bazel by downloading the currently
+# supported version, and then calling it. This way, we can make sure
+# that running bazel will always get meaningful results, at least
+# until Bazel 1.0 is released.
+
+set -e
+
+VERSION=0.24.1
+
+CWD=`pwd`
+BASEURL=https://github.com/bazelbuild/bazel/releases/download/
+cd `dirname $0`
+TOOLDIR=`pwd`
+
+case `uname -sm` in
+  "Linux x86_64")
+    suffix=linux-x86_64
+    ;;
+  "Darwin x86_64")
+    suffix=darwin-x86_64
+    ;;
+  *)
+    echo "Unsupported architecture: `uname -sm`"
+    exit 1
+    ;;
+esac
+
+filename=bazel-$VERSION-$suffix
+
+if [ ! -x $filename ] ; then
+  curl -L $BASEURL/$VERSION/$filename > $filename
+  chmod a+x $filename
+fi
+
+cd $CWD
+$TOOLDIR/$filename $@
diff --git a/tools/codegen/core/gen_static_metadata.py b/tools/codegen/core/gen_static_metadata.py
index 5545e871117..d66fdc3e835 100755
--- a/tools/codegen/core/gen_static_metadata.py
+++ b/tools/codegen/core/gen_static_metadata.py
@@ -376,6 +376,8 @@ print >> H, '#define GRPC_CORE_LIB_TRANSPORT_STATIC_METADATA_H'
 print >> H
 print >> H, '#include <grpc/support/port_platform.h>'
 print >> H
+print >> H, '#include <cstdint>'
+print >> H
 print >> H, '#include "src/core/lib/transport/metadata.h"'
 print >> H
 print >> C, '#include <grpc/support/port_platform.h>'
@@ -433,8 +435,8 @@ for i, elem in enumerate(all_strs):
 print >> C, '};'
 print >> C
 print >> H, '#define GRPC_STATIC_METADATA_INDEX(static_slice) \\'
-print >> H, ('  ((int)((static_slice).refcount - '
-             'grpc_static_metadata_refcounts))')
+print >> H, ('  (static_cast<intptr_t>(((static_slice).refcount - '
+             'grpc_static_metadata_refcounts)))')
 print >> H
 
 print >> D, '# hpack fuzzing dictionary'
@@ -537,10 +539,10 @@ print >> C, 'static const uint8_t elem_idxs[] = {%s};' % ','.join(
     '%d' % i for i in idxs)
 print >> C
 
-print >> H, 'grpc_mdelem grpc_static_mdelem_for_static_strings(int a, int b);'
-print >> C, 'grpc_mdelem grpc_static_mdelem_for_static_strings(int a, int b) {'
+print >> H, 'grpc_mdelem grpc_static_mdelem_for_static_strings(intptr_t a, intptr_t b);'
+print >> C, 'grpc_mdelem grpc_static_mdelem_for_static_strings(intptr_t a, intptr_t b) {'
 print >> C, '  if (a == -1 || b == -1) return GRPC_MDNULL;'
-print >> C, '  uint32_t k = (uint32_t)(a * %d + b);' % len(all_strs)
+print >> C, '  uint32_t k = static_cast<uint32_t>(a * %d + b);' % len(all_strs)
 print >> C, '  uint32_t h = elems_phash(k);'
 print >> C, '  return h < GPR_ARRAY_SIZE(elem_keys) && elem_keys[h] == k && elem_idxs[h] != 255 ? GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[elem_idxs[h]], GRPC_MDELEM_STORAGE_STATIC) : GRPC_MDNULL;'
 print >> C, '}'
@@ -566,7 +568,7 @@ print >> H, '  } named;'
 print >> H, '} grpc_metadata_batch_callouts;'
 print >> H
 print >> H, '#define GRPC_BATCH_INDEX_OF(slice) \\'
-print >> H, '  (GRPC_IS_STATIC_METADATA_STRING((slice)) ? (grpc_metadata_batch_callouts_index)GPR_CLAMP(GRPC_STATIC_METADATA_INDEX((slice)), 0, GRPC_BATCH_CALLOUTS_COUNT) : GRPC_BATCH_CALLOUTS_COUNT)'
+print >> H, '  (GRPC_IS_STATIC_METADATA_STRING((slice)) ? static_cast<grpc_metadata_batch_callouts_index>(GPR_CLAMP(GRPC_STATIC_METADATA_INDEX((slice)), 0, static_cast<intptr_t>(GRPC_BATCH_CALLOUTS_COUNT))) : GRPC_BATCH_CALLOUTS_COUNT)'
 print >> H
 
 print >> H, 'extern const uint8_t grpc_static_accept_encoding_metadata[%d];' % (
diff --git a/tools/distrib/python/grpcio_tools/grpc_version.py b/tools/distrib/python/grpcio_tools/grpc_version.py
index 22d04c5a1af..24ec4301b65 100644
--- a/tools/distrib/python/grpcio_tools/grpc_version.py
+++ b/tools/distrib/python/grpcio_tools/grpc_version.py
@@ -14,4 +14,4 @@
 
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/tools/distrib/python/grpcio_tools/grpc_version.py.template`!!!
 
-VERSION = '1.21.0.dev0'
+VERSION = '1.22.0.dev0'
diff --git a/tools/dockerfile/interoptest/grpc_interop_aspnetcore/build_interop.sh b/tools/dockerfile/interoptest/grpc_interop_aspnetcore/build_interop.sh
index 2a3e6f3a0ee..65e848ded32 100644
--- a/tools/dockerfile/interoptest/grpc_interop_aspnetcore/build_interop.sh
+++ b/tools/dockerfile/interoptest/grpc_interop_aspnetcore/build_interop.sh
@@ -39,5 +39,4 @@ fi
 
 ./build/get-grpc.sh
 
-cd testassets/InteropTestsWebsite
-dotnet build --configuration Debug
+dotnet build --configuration Debug Grpc.AspNetCore.sln
diff --git a/tools/dockerfile/interoptest/grpc_interop_node/build_interop.sh b/tools/dockerfile/interoptest/grpc_interop_node/build_interop.sh
index c16efc1d354..aeb82e0c9c3 100755
--- a/tools/dockerfile/interoptest/grpc_interop_node/build_interop.sh
+++ b/tools/dockerfile/interoptest/grpc_interop_node/build_interop.sh
@@ -29,6 +29,4 @@ cp -r /var/local/jenkins/service_account $HOME || true
 cd /var/local/git/grpc-node
 
 # build Node interop client & server
-npm install -g node-gyp gulp
-npm install
-gulp setup
+./setup_interop.sh
diff --git a/tools/dockerfile/interoptest/grpc_interop_nodepurejs/build_interop.sh b/tools/dockerfile/interoptest/grpc_interop_nodepurejs/build_interop.sh
index d41ccacd2f9..db55f5a19f3 100755
--- a/tools/dockerfile/interoptest/grpc_interop_nodepurejs/build_interop.sh
+++ b/tools/dockerfile/interoptest/grpc_interop_nodepurejs/build_interop.sh
@@ -29,8 +29,4 @@ cp -r /var/local/jenkins/service_account $HOME || true
 cd /var/local/git/grpc-node
 
 # build Node interop client & server
-npm install -g gulp
-npm install
-gulp js.core.install
-gulp protobuf.install
-gulp internal.test.install
+./setup_interop_purejs.sh
diff --git a/tools/doxygen/Doxyfile.c++ b/tools/doxygen/Doxyfile.c++
index d5874920752..667b9b3541e 100644
--- a/tools/doxygen/Doxyfile.c++
+++ b/tools/doxygen/Doxyfile.c++
@@ -40,7 +40,7 @@ PROJECT_NAME           = "GRPC C++"
 # could be handy for archiving the generated documentation or if some version
 # control system is used.
 
-PROJECT_NUMBER         = 1.21.0-dev
+PROJECT_NUMBER         = 1.22.0-dev
 
 # Using the PROJECT_BRIEF tag one can provide an optional one line description
 # for a project that appears at the top of each page and should give viewer a
diff --git a/tools/doxygen/Doxyfile.c++.internal b/tools/doxygen/Doxyfile.c++.internal
index ab0968b3252..529b35a2c39 100644
--- a/tools/doxygen/Doxyfile.c++.internal
+++ b/tools/doxygen/Doxyfile.c++.internal
@@ -40,7 +40,7 @@ PROJECT_NAME           = "GRPC C++"
 # could be handy for archiving the generated documentation or if some version
 # control system is used.
 
-PROJECT_NUMBER         = 1.21.0-dev
+PROJECT_NUMBER         = 1.22.0-dev
 
 # Using the PROJECT_BRIEF tag one can provide an optional one line description
 # for a project that appears at the top of each page and should give viewer a
@@ -1188,6 +1188,7 @@ src/core/lib/slice/percent_encoding.h \
 src/core/lib/slice/slice_hash_table.h \
 src/core/lib/slice/slice_internal.h \
 src/core/lib/slice/slice_string_helpers.h \
+src/core/lib/slice/slice_utils.h \
 src/core/lib/slice/slice_weak_hash_table.h \
 src/core/lib/surface/api_trace.h \
 src/core/lib/surface/call.h \
diff --git a/tools/doxygen/Doxyfile.core.internal b/tools/doxygen/Doxyfile.core.internal
index b34c7734621..0365f284573 100644
--- a/tools/doxygen/Doxyfile.core.internal
+++ b/tools/doxygen/Doxyfile.core.internal
@@ -951,8 +951,6 @@ src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_fallba
 src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_libuv.cc \
 src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_posix.cc \
 src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_windows.cc \
-src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.cc \
-src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.h \
 src/core/ext/filters/client_channel/resolver/dns/native/README.md \
 src/core/ext/filters/client_channel/resolver/dns/native/dns_resolver.cc \
 src/core/ext/filters/client_channel/resolver/fake/fake_resolver.cc \
@@ -1449,6 +1447,7 @@ src/core/lib/slice/slice_intern.cc \
 src/core/lib/slice/slice_internal.h \
 src/core/lib/slice/slice_string_helpers.cc \
 src/core/lib/slice/slice_string_helpers.h \
+src/core/lib/slice/slice_utils.h \
 src/core/lib/slice/slice_weak_hash_table.h \
 src/core/lib/surface/README.md \
 src/core/lib/surface/api_trace.cc \
diff --git a/tools/run_tests/generated/sources_and_headers.json b/tools/run_tests/generated/sources_and_headers.json
index 39ee76b1a9c..2754bf2171e 100644
--- a/tools/run_tests/generated/sources_and_headers.json
+++ b/tools/run_tests/generated/sources_and_headers.json
@@ -2776,6 +2776,56 @@
     "third_party": false, 
     "type": "target"
   }, 
+  {
+    "deps": [
+      "benchmark", 
+      "bm_callback_test_service_impl", 
+      "gpr", 
+      "grpc++_test_config", 
+      "grpc++_test_util_unsecure", 
+      "grpc++_unsecure", 
+      "grpc_benchmark", 
+      "grpc_test_util_unsecure", 
+      "grpc_unsecure"
+    ], 
+    "headers": [
+      "test/cpp/microbenchmarks/callback_streaming_ping_pong.h"
+    ], 
+    "is_filegroup": false, 
+    "language": "c++", 
+    "name": "bm_callback_streaming_ping_pong", 
+    "src": [
+      "test/cpp/microbenchmarks/bm_callback_streaming_ping_pong.cc", 
+      "test/cpp/microbenchmarks/callback_streaming_ping_pong.h"
+    ], 
+    "third_party": false, 
+    "type": "target"
+  }, 
+  {
+    "deps": [
+      "benchmark", 
+      "bm_callback_test_service_impl", 
+      "gpr", 
+      "grpc++_test_config", 
+      "grpc++_test_util_unsecure", 
+      "grpc++_unsecure", 
+      "grpc_benchmark", 
+      "grpc_test_util_unsecure", 
+      "grpc_unsecure"
+    ], 
+    "headers": [
+      "test/cpp/microbenchmarks/callback_unary_ping_pong.h"
+    ], 
+    "is_filegroup": false, 
+    "language": "c++", 
+    "name": "bm_callback_unary_ping_pong", 
+    "src": [
+      "test/cpp/microbenchmarks/bm_callback_unary_ping_pong.cc", 
+      "test/cpp/microbenchmarks/callback_unary_ping_pong.h"
+    ], 
+    "third_party": false, 
+    "type": "target"
+  }, 
   {
     "deps": [
       "benchmark", 
@@ -6624,6 +6674,33 @@
     "third_party": false, 
     "type": "lib"
   }, 
+  {
+    "deps": [
+      "benchmark", 
+      "gpr", 
+      "grpc++_test_config", 
+      "grpc++_test_util_unsecure", 
+      "grpc++_unsecure", 
+      "grpc_benchmark", 
+      "grpc_test_util_unsecure", 
+      "grpc_unsecure"
+    ], 
+    "headers": [
+      "src/proto/grpc/testing/echo.grpc.pb.h", 
+      "src/proto/grpc/testing/echo.pb.h", 
+      "src/proto/grpc/testing/echo_mock.grpc.pb.h", 
+      "test/cpp/microbenchmarks/callback_test_service.h"
+    ], 
+    "is_filegroup": false, 
+    "language": "c++", 
+    "name": "bm_callback_test_service_impl", 
+    "src": [
+      "test/cpp/microbenchmarks/callback_test_service.cc", 
+      "test/cpp/microbenchmarks/callback_test_service.h"
+    ], 
+    "third_party": false, 
+    "type": "lib"
+  }, 
   {
     "deps": [], 
     "headers": [
@@ -8574,6 +8651,7 @@
       "src/core/lib/slice/slice_hash_table.h", 
       "src/core/lib/slice/slice_internal.h", 
       "src/core/lib/slice/slice_string_helpers.h", 
+      "src/core/lib/slice/slice_utils.h", 
       "src/core/lib/slice/slice_weak_hash_table.h", 
       "src/core/lib/surface/api_trace.h", 
       "src/core/lib/surface/call.h", 
@@ -8730,6 +8808,7 @@
       "src/core/lib/slice/slice_hash_table.h", 
       "src/core/lib/slice/slice_internal.h", 
       "src/core/lib/slice/slice_string_helpers.h", 
+      "src/core/lib/slice/slice_utils.h", 
       "src/core/lib/slice/slice_weak_hash_table.h", 
       "src/core/lib/surface/api_trace.h", 
       "src/core/lib/surface/call.h", 
@@ -9173,8 +9252,7 @@
     "deps": [
       "gpr", 
       "grpc_base", 
-      "grpc_client_channel", 
-      "grpc_resolver_dns_selection"
+      "grpc_client_channel"
     ], 
     "headers": [
       "src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver.h", 
@@ -9204,8 +9282,7 @@
     "deps": [
       "gpr", 
       "grpc_base", 
-      "grpc_client_channel", 
-      "grpc_resolver_dns_selection"
+      "grpc_client_channel"
     ], 
     "headers": [], 
     "is_filegroup": true, 
@@ -9217,24 +9294,6 @@
     "third_party": false, 
     "type": "filegroup"
   }, 
-  {
-    "deps": [
-      "gpr", 
-      "grpc_base"
-    ], 
-    "headers": [
-      "src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.h"
-    ], 
-    "is_filegroup": true, 
-    "language": "c", 
-    "name": "grpc_resolver_dns_selection", 
-    "src": [
-      "src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.cc", 
-      "src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.h"
-    ], 
-    "third_party": false, 
-    "type": "filegroup"
-  }, 
   {
     "deps": [
       "gpr", 
diff --git a/tools/run_tests/generated/tests.json b/tools/run_tests/generated/tests.json
index c156c8347ae..930f7f8748d 100644
--- a/tools/run_tests/generated/tests.json
+++ b/tools/run_tests/generated/tests.json
@@ -3479,6 +3479,50 @@
     ], 
     "uses_polling": false
   }, 
+  {
+    "args": [], 
+    "benchmark": true, 
+    "ci_platforms": [
+      "linux", 
+      "mac", 
+      "posix"
+    ], 
+    "cpu_cost": 1.0, 
+    "exclude_configs": [], 
+    "exclude_iomgrs": [], 
+    "flaky": false, 
+    "gtest": false, 
+    "language": "c++", 
+    "name": "bm_callback_streaming_ping_pong", 
+    "platforms": [
+      "linux", 
+      "mac", 
+      "posix"
+    ], 
+    "uses_polling": true
+  }, 
+  {
+    "args": [], 
+    "benchmark": true, 
+    "ci_platforms": [
+      "linux", 
+      "mac", 
+      "posix"
+    ], 
+    "cpu_cost": 1.0, 
+    "exclude_configs": [], 
+    "exclude_iomgrs": [], 
+    "flaky": false, 
+    "gtest": false, 
+    "language": "c++", 
+    "name": "bm_callback_unary_ping_pong", 
+    "platforms": [
+      "linux", 
+      "mac", 
+      "posix"
+    ], 
+    "uses_polling": true
+  }, 
   {
     "args": [], 
     "benchmark": true, 
diff --git a/tools/run_tests/run_interop_tests.py b/tools/run_tests/run_interop_tests.py
index 567c628d8e0..cc6901bdebe 100755
--- a/tools/run_tests/run_interop_tests.py
+++ b/tools/run_tests/run_interop_tests.py
@@ -192,7 +192,7 @@ class CSharpCoreCLRLanguage:
 class AspNetCoreLanguage:
 
     def __init__(self):
-        self.client_cwd = '../grpc-dotnet'
+        self.client_cwd = '../grpc-dotnet/testassets/InteropTestsClient/bin/Debug/netcoreapp3.0'
         self.server_cwd = '../grpc-dotnet/testassets/InteropTestsWebsite/bin/Debug/netcoreapp3.0'
         self.safename = str(self)
 
@@ -200,8 +200,7 @@ class AspNetCoreLanguage:
         return {}
 
     def client_cmd(self, args):
-        # attempt to run client should fail
-        return ['dotnet' 'exec', 'CLIENT_NOT_SUPPORTED'] + args
+        return ['dotnet', 'exec', 'InteropTestsClient.dll'] + args
 
     def server_cmd(self, args):
         return ['dotnet', 'exec', 'InteropTestsWebsite.dll'] + args
@@ -210,8 +209,10 @@ class AspNetCoreLanguage:
         return {}
 
     def unimplemented_test_cases(self):
-        # aspnetcore doesn't have a client so ignore all test cases.
-        return _TEST_CASES + _AUTH_TEST_CASES
+        return _SKIP_COMPRESSION + \
+            _SKIP_SPECIAL_STATUS_MESSAGE + \
+            _AUTH_TEST_CASES + \
+            ['cancel_after_first_response', 'ping_pong']
 
     def unimplemented_test_cases_server(self):
         return _SKIP_COMPRESSION + _SKIP_SPECIAL_STATUS_MESSAGE
diff --git a/tools/run_tests/run_microbenchmark.py b/tools/run_tests/run_microbenchmark.py
index a7fde3007af..4e4d05cdcd4 100755
--- a/tools/run_tests/run_microbenchmark.py
+++ b/tools/run_tests/run_microbenchmark.py
@@ -96,7 +96,7 @@ def collect_latency(bm_name, args):
                     '--benchmark_filter=^%s$' % line,
                     '--benchmark_min_time=0.05'
                 ],
-                environ={'GRPC_LATENCY_TRACE': '%s.trace' % fnize(line)},
+                environ={'LATENCY_TRACE': '%s.trace' % fnize(line)},
                 shortname='profile-%s' % fnize(line)))
         profile_analysis.append(
             jobset.JobSpec(
diff --git a/tools/run_tests/sanity/core_banned_functions.py b/tools/run_tests/sanity/core_banned_functions.py
index ce9ff0dae21..549ae14f5ab 100755
--- a/tools/run_tests/sanity/core_banned_functions.py
+++ b/tools/run_tests/sanity/core_banned_functions.py
@@ -45,6 +45,10 @@ BANNED_EXCEPT = {
     'grpc_closure_sched(': ['src/core/lib/iomgr/closure.cc'],
     'grpc_closure_run(': ['src/core/lib/iomgr/closure.cc'],
     'grpc_closure_list_sched(': ['src/core/lib/iomgr/closure.cc'],
+    'gpr_getenv_silent(': [
+        'src/core/lib/gpr/log.cc', 'src/core/lib/gpr/env_linux.cc',
+        'src/core/lib/gpr/env_posix.cc', 'src/core/lib/gpr/env_windows.cc'
+    ],
 }
 
 errors = 0